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Plesioastiotrema monticellii (Stossich, 1904) n. comb. (Figs. 1–3) (Syns. Distomum signatum of Monticelli, 1891 nec Dujardin, 1845; Astiotrema monticellii Stossich, 1904) Records. 1. Stossich (1904); 2. Dollfus (1957); 3. Timofeeva (1961); 4. Sharpilo & Iskova (1989); 5. Tkach et al. (2001); 6. Ruchin & Kirillov (2012). Remarks. Plesioastiotrema monticellii n. comb. (syn. A. monticellii) was incompletely described as Distomum signatum Dujardin, 1845 by Monticelli (1891). Stossich (1904) re-examined the materials deposited by Monticelli and assigned them to Astiotrema as A. monticellii which, in turn, is presently reassigned as the type-species of Plesioastiotrema. From previous records of this species, only the anterior extent of the vitelline fields exhibited a slight range of variability where the follicles either reached the anterior border of the ovary (Dollfus 1957), extended a little further to a point midway between the ovary and intestinal bifurcation (Stossich 1904; Dollfus 1957) or the follicles extended to immediately posterior to the intestinal bifurcation (Timofeeva 1961; Sharpilo & Iskova 1989). Madhavi & Rao (1972) reported a doubtful record of A. monticellii (= P. monticellii) from the intestine of the Indian flap-shelled turtle, Lissemys punctata (Bonnaterre) (Testudines: Trionychidae), collected from an unidentified locality (we assume Asia). Lissemys punctata is restricted to Asian localities (e.g., Bangladesh, Burma, India, Nepal, Pakistan & Sri Lanka) (see Uetz et al. 2022) and represents a known host for A. reniferum, Astiotrema odhneri Bhalerao, 1936 and Astiotrema cyclemysi Siddiqi, 1965 (see Gupta 1954; Agrawal 1966a; Karar et al. 2021); whilst the other records of P. monticellii clarify the limit of its distribution to European localities and to parasitize only colubrid water snakes (Stossich 1904; Dollfus 1957; Timofeeva 1961; Sharpilo & Iskova 1989; Tkach et al. 2001; Ruchin & Kirillov 2012). Based on the distinct and limited distribution of host groups, the distant localities, and the absence of both a complete morphological description and illustrations for the adult worms of Madhavi & Rao (1972), we believe they misidentified their specimens. Accepted records of P. monticellii demonstrate its uniquity in morphology and limited locality (Europe) as well as its distinct host group (colubrid water snakes). Plesioastiotrema monticellii can be easily characterized within the new genus by the following combination of morphological features: (i) oral sucker larger than ventral one, (ii) vitelline field short, extends anteriorly to either ovarian level or level immediately posterior to intestinal bifurcation while posteriorly follicles terminate at mid-level of anterior testis, (iii) ceca short, terminate at level of inter-testicular space, and (iv) testes that are tandem and ellipsoid in shape., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2023, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: Taxa excluded from Astiotrema (sensu stricto) with special reference to plagiorchioid genera closely related to the restricted concept of Astiotrema, pp. 445-495 in Zootaxa 5284 (3) on pages 448-450, DOI: 10.11646/zootaxa.5284.3.2, http://zenodo.org/record/7929507, {"references":["Stossich, M. (1904) Alcuni distomi della collezione elmintologica del Museo Zoologico di Napoli. Annuario del Museo Zoologica della R. Universita di Napoli, 1, 1 - 14.","̕ Monticelli, F. S. (1891) Osservazioni intorno ad alcune forme del gen. Apoblema Dujard. Atti della Reale Accademia delle Scienze, Torino, 26, 340 - 368.","Dujardin, F. (1845) Histoire naturelle des helminthes ou vers intestinaux. Librarie Encylopedique de Roret, Paris, 654 pp. https: // doi. org / 10.5962 / bhl. title. 10123","Dollfus, R. - P. (1957) Three Distoma (Telorchis, Opisthioglyphe, Astiotrema) from snakes of the genus Natrix Laurenti 1768. Annales de Parasitologie Humaine et Comparee, 32, 41 - 55.","Timofeeva, T. (1961) Astiotrema monticelli (Plagiorchidae) in the USSR. Trudy Gel'mintologicheskoi Laboratorii. Akademiya Nauk SSSR, 11, 299 - 302.","Sharpilo V. P. & Iskova N. I. (1989) Fauna of the Ukraine. Vol. 34. Trematoda. Part 3. Plagiorchiata. Naukova Dumka, Kiev, 279 pp. [in Russian]","Tkach, V. V., Pawlowski, J., Mariaux, J., Swiderski, Z., Littlewood, D. T. J. & Bray, R. A. (2001) Molecular phylogeny of the suborder Plagiorchiata and its position in the system of Digenea. In: Littlewood, D. T. J. & Bray, R. A. (Eds.), Interrelationships of the Platyhelminthes. Taylor & Francis, London, pp. 186 - 193.","Ruchin, A. B. & Kirillov, A. A. (2012) Helminth (Natrix natrix L.) common snake of Mordovia. Biological Sciences of Kazakhstan, 3, 30 - 37. [in Russian]","Madhavi, R. & Rao, K. H. (1972) A specimen of Astiotrema monticellii Stossich, 1904, with anomalous female reproductive system. The Journal of Parasitology, 58, 1012 - 1014. https: // doi. org / 10.2307 / 3286609","Uetz, P., Freed, P. & Hosek, J. (Eds.) (2022) The Reptile Database. Available from: http: // www. reptile-database. org (accessed 1 July 2022)","Bhalerao, G. D. (1936) Studies on the helminths of India. Trematoda II. Journal of Helminthology, 14, 181 - 206. https: // doi. org / 10.1017 / s 0022149 x 00004089","Siddiqi, A. H. (1965) A new species of the genus Astiotrema Looss, 1900 with a key to its species. Journal of Helminthology, 39, 113 - 116. https: // doi. org / 10.1017 / s 0022149 x 00020101","Gupta, N. K. (1954) On five new trematodes of the genus Astiotrema Looss, 1900, from the intestine of Lissemys punctata punctata and discussion on the synonymity of two already known forms. Research Bulletin of the Panjab University, 49 / 50, 85 - 100.","Agrawal, V. (1966 a) Four trematode parasites (Plagiorchiidae Luhe, 1901 emend. Ward, 1917) from reptiles of Lucknow. Revista de Biologia Tropical, 14, 133 - 151. Agrawal, V. (1966 b) Studies on some trematode parasites of fresh water fishes from Lucknow. Annales de Parasitologie Humaine et Comparee, 41, 217 - 231. https: // doi. org / 10.1051 / parasite / 1966413217","Karar, Y. F. M., Blend, C. K., Dronen, N. P. & Adel, A. (2021) Towards resolving the problematic status of the digenean genus Astiotrema Looss, 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto). Zootaxa, 4991 (1), 36 - 72. https: // doi. org / 10.11646 / zootaxa. 4991.1.2"]}

Laiogonimus tananarivensis (Deblock & Capron, 1962) Fischthal & Thomas, 1968 (Figs. 14–16) (Syns. Astiotrema [Biguetrema] tananarivense Deblock & Capron, 1962; Astiotrema tananarivense Deblock & Capron, 1962; Laiogonimus vercammengrandjeani Meskal, 1970 n. syn.) Records. 1. Deblock & Capron (1962); 2. Meskal (1970). Remarks. Biguetrema was erected by Deblock & Capron (1962) as a subgenus within Astiotrema for the type species Astiotrema (Biguetrema) tananarivense to accommodate specimens collected from the intestine of the Mascarene grass or ridged frog, Ptychadena mascareniensis (Duméril & Bibron) (syn. Rana mascareniensis Duméril & Bibron) (Anura: Ptychadenidae) (type-host), Goudot’s bright-eyed frog, Boophis goudotii Tschudi (Syn. Rhacophorus goudoti Tschudi) (Anura: Mantellidae), and from an unidentified shrub frog, Rhacophorus sp. (Anura: Rhacophoridae), from Madagascar. Deblock & Capron (1962) stated that their specimens were morphologically similar to members of Astiotrema except in having four distinct features, the combination of which has not been reported before in Astiotrema or in the closely-related taxa Haplometra Looss, 1899, Glossidium, Alloglossidium Simer, 1929, Styphlodora Looss, 1899, and Paurophyllum Byrd, Parker & Reiber, 1940. These four features were (i) a cirrus-pouch that extends within the forebody obliquely from the anterior margin of the ventral sucker, (ii) a seminal vesicle folded over itself followed by a spherical pars prostatica, (iii) a pre-bifurcal, sinistral genital pore, and (iv) lateral, mostly extracecal vitellarium composed of 6 to 12 voluminous, massive follicles. In addition, due to the report of Astiotrema trituri Grabda, 1959 (= Neoastiotrema trituri [Grabda, 1959] Tkach, 2008) by Grabda (1959a, 1959b) from an amphibian (i.e., L. vulgaris – see above), Deblock & Capron (1962) erected Biguetrema as a subgenus within Astiotrema. Fischthal & Thomas (1968) excluded A. (B.) tananarivense from Astiotrema and combined it within Laiogonimus as the second recorded species, L. tananarivensis, characterizing it by having testes not completely surrounded by the uterus, a seminal vesicle with one loop, and the oral sucker smaller than the ventral one. Meskal (1970) revised A. (B.) tananarivense and referred to conspicuous differences distinguishing it from Astiotrema in several respects: (i) possessing a cirrus-pouch that does not surpass the level of the mid-ventral sucker posteriorly vs a cirrus-pouch in Astiotrema which extends into the hindbody, reaching the ovarian level posteriorly; (ii) having a distinctly submedian to nearly submarginal genital pore whereas Astiotrema has a median to slightly submedian genital pore; (iii) the cirrus-pouch in A. (B.) tananarivense contains a winding to convoluted seminal vesicle vs a unipartite sacciform one in Astiotrema; and (iv) an ovary much closer to the ventral sucker than the anterior testis in A. (B.) tananarivense while the ovary is mid-way between the ventral sucker and anterior testis in taxa of Astiotrema. Based on those differential characteristics, Meskal (1970) adopted A. (B.) tananarivense within Laiogonimus, concurring with Fischthal & Thomas (1968) regarding their combination L. tananarivensis . Yamaguti (1971) followed the same approach and synonymized the subgenus, Biguetrema, within Laiogonimus based on their similarities in morphology, host group (anuran amphibians) and locality (both taxa are from Africa, specifically Madagascar and Lake Kivu on the border between the Democratic Republic of the Congo and Rwanda) (see Vercammen-Grandjean 1960; Deblock & Capron 1962). Dhar (1977) considered this species to belong within Astiotrema (i.e., A. tananarivense), apparently unaware of the synonymy within Laiogonimus. We support the placement of A. (B.) tananarivense within Laiogonimus as L. tananarivensis based on previously explained morphological features and host-parasite data, in addition to the distinctive nature of the vitellarium observed in L. tananarivensis: vitellarium consists of large follicles distributed in two lateral, mostly extra-cecal groups of 6 to 12 follicles per row, extending along ceca between ventral sucker and posterior testis; vitelline follicle numbers usually higher in the left group compared to the right one, while follicle number on the right side varies more than that on the left (see Deblock & Capron 1962). Meskal (1970) described the third species within Laiogonimus, L. vercammengrandjeani, for specimens gathered from the small intestine, occasionally rectum, of some anuran amphibians in Ethiopia: the Mascarene grass or ridged frog, P. mascareniensis; the Erlanger’s grassland frog, Ptychadena erlangeri (Ahl) (Anura: Ptychadenidae); Natal dwarf puddle frog, Phrynobatrachus natalensis (Smith) (Anura: Phrynobatrachidae); and Angola river frog or common river frog, Amietia angolensis (Bocage) (syn. Rana angolensis Bocage) (Anura: Pyxicephalidae). Laiogonimus vercammengrandjeani was distinguished from L. tananarivensis by possessing an esophagus shorter than the pharynx, slightly larger egg size (30.0–32.8; 31.3 × 12.5 µm in L. vercammengrandjeani v s 24.0 –28.0; 24.5 × 15.0–18.0; 15.5 µm in L. tananarivensis), slightly smaller suckers ratio (1: 1.20–1.30 in L. vercammengrandjeani v s 1: 1.43 in L. tananarivensis) and shorter body length (1,350–1,700; 1,508 µm in L. vercammengrandjeani vs 2,99 – 3,800; 3,440 µm in L. tananarivensis). We believe these variations represent slight allometric changes which can be attributed to one or a combination of several factors, in particular, maturity of the worm, degree of contraction and flattening of the sample(s), fixation-induced variation, host induced variability (i.e., slight difference in egg size) and different treatments of the specimens such as dehydration and staining methods. Accordingly, with given morphological and morphometric measurements, the same host (P. mascareniensis), close morpho and nearby localities in Africa (Ethiopia vs Madagascar); we consider L. vercammengrandjeani a synonym of L. tananarivensis., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2023, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: Taxa excluded from Astiotrema (sensu stricto) with special reference to plagiorchioid genera closely related to the restricted concept of Astiotrema, pp. 445-495 in Zootaxa 5284 (3) on pages 461-463, DOI: 10.11646/zootaxa.5284.3.2, http://zenodo.org/record/7929507, {"references":["Deblock, S. & Capron, A. (1962) Description d' Astiotrema (Biguetrema) tananarivense n. subgen., Plagiorchiidae intestinal d'Amphibiens malgaches. Annales de Parasitologie Humaine et Comparee, 37, 97 - 107. ̕ https: // doi. org / 10.1051 / parasite / 1962371097","Fischthal, J. H. & Thomas, J. D. (1968) Digenetic trematodes of amphibians and reptiles from Ghana. Proceedings of the Helminthological Society of Washington, 35, 1 - 15.","Meskal, F. H. (1970) Trematodes of anurans from Ethiopia. Arbok for Universiteteti Bergensis. Mathematica-Naturvum Series, 1, 1 - 73.","Looss, A. (1899) Weitere Beitrage zur Kenntnis der Trematoden-fauna Aegyptens, zugleich Versuch einer naturlichen Gliederung des Genus Distomum Retzius. Zoologische Jahrbucher, 12, 521 - 784. https: // doi. org / 10.5962 / bhl. part. 2037","Tkach, V. V. (2008) Family Plagiorchiidae Luhe, 1901. In: Bray, R. A., Gibson, D. I. & Jones, A. (Eds.), Keys to the Trematoda. Vol. 3. CABI Publishing and the Natural History Museum, Wallingford, pp. 295 - 325. https: // doi. org / 10.1079 / 9780851995885.0295","Grabda, B. (1959 a) Astiotrema trituri sp. n. (Trematoda-Plagiorchiidae) from the small intestine of Triturus vulgaris L. Bulletin de l'Academie polonaise des Sciences. Classe II. Serie des Sciences Biologiques, 7, 17 - 21.","Grabda, B. (1959 b) The life-cycle of Astiotrema trituri B. Grabda, 1959 (Trematoda; Plagiorchiidae). Acta Parasitologica Polonica, 7, 489 - 498.","Yamaguti, S. (1971) Synopsis of Digenetic Trematodes of Vertebrates. Vols. I & II. Keigaku Publishing Company, Tokyo, 1423 pp.","Vercammen-Grandjean, P. H. (1960) Introduction a un essai de classification rationnelle des larves de Trombiculinae Ewing, 1944 (Acarina-Trombiculidae). Acarologia, 2, 469 - 471.","Dhar, R. L. (1977) Astiotrema fotedari n. sp. (Trematoda: Plagiorchidae Luhe, 1901) from the intestine of Labeo dero (Hemilton). Journal of Science, University of Kashmir, 3, 99 - 104."]}

Neoastiotrema trituri (Grabda, 1959) Tkach, 2008 (Fig. 17) (Syn. Astiotrema trituri Grabda, 1959) Records. 1. Grabda (1959a, 1959b); 2. Sharpilo & Iskova (1989); 3. Tkach (2008). Remarks. Grabda (1959a) described A. trituri from the small intestine of the smooth, northern smooth or common newt, Lissotriton vulgaris (Linnaeus) (syn. Triturus vulgaris Dunn) (Caudata: Salamandridae), from Lake Mamry in northeastern Poland. Astiotrema trituri was distinguished from all Astiotrema species by (i) the position of the posterior testis near the posterior extremity of the body and posterior to the ends of the ceca, (ii) the much smaller cirrus pouch, and (iii) very large eggs – “almost double-sized” (48–61; 54 × 25–31; 29). That same year, Grabda (1959b) elucidated that A. trituri has life-cycle patterns identical to that of members of the Plagiorchioidea and concluded that the first intermediate host was a pulmonate snail, the great ramshorn, Planorbarius corneus (Linnaeus) (syn. Coretus corneus [Linnaeus]) (Gastropoda: Planorbidae). The second intermediate hosts included some cladoceran species: Simocephalus exspinosus (De Geer), Ceriodaphnia reticulata (Jurine), Daphnia magna Straus (Anomopoda: Daphniidae) and Eurycercus lamellatus (Müller) (Anomopoda: Eurycercidae). The development of this parasite includes the formation of a sporocyst and a xiphidiocercaria. Molecular characterization by Tkach (2008) of some taxa of Astiotrema including A. reniferum , A. monticellii (= P. monticellii), A. turneri (= H. turneri) and A. trituri demonstrated that the first three taxa formed a monophyletic clade closest to the heterophyids in contrast to A. trituri which clustered very close to Plagiorchis Lühe, 1899. Concerning A. trituri , it possesses a typical plagiorchiid-like bipartite seminal vesicle, whereas the other three species of Astiotrema (sensu lato) in the analysis of Tkach (2008) possess an undivided, sac-like seminal vesicle. Based on life-cycle patterns of A. monticellii (= P. monticellii) examined by Shevchenko & Vergun (1960), Tkach (2008) referred that: (i) the first intermediate host of A. monticellii (= P. monticellii) is the prosobranch (gilled) snail Bithynia leachii (Sheppard) (Gastropoda: Bithyniidae), not a pulmonate one as described for A. trituri; (ii) amphibians serve as the definitive host for A. trituri (see Grabda 1959b) whereas amphibians represent intermediate hosts for A. monticellii (= P. monticellii) (Shevchenko & Vergun 1960); and (iii) the development of A. monticellii (= P. monticellii) includes the formation of cercariae from the Pleurolophocerca group within rediae (see Shevchenko & Vergun 1960), which is typical for members of the Opisthorchioidea. As previous molecular phylogenetic analyses generally indicated that Astiotrema formed a monophyletic clade distinctly separate from all members of the Plagiorchioidea and that clade was, moreover, closer to the Opisthorchioidea (Tkach et al. 2001; Olson et al. 2003), Tkach (2008) removed A. trituri from Astiotrema and transferred it into the Plagiorchiidae. Despite the high similarity between A. trituri and members of Plagiorchis, the position of the right posterior testis (near the posterior extremity and past the cecal ends) vs the left anterior testis (intercecal and separated from right posterior testis by numerous uterine coils) gave justification for separating A. trituri into its own genus, Neoastiotrema, with its type- and only species, N. trituri (see Tkach 2008). Besprozvannykh et al. (2015) demonstrated that Shevchenko & Vergun (1960) most likely described a larva belonging to a member of the Opisthorchioidea and neither the cercaria nor the metacercaria of a species of Astiotrema. In addition, they clarified that the first intermediate host of A. odhneri is a pulmonate snail and not a prosobranch (gilled) one; whereas, the second intermediate host can include pulmonate snails, frog tadpoles, and small fish within which sporocysts and xiphidiocercariae develop, but neither rediae nor pleurolophocercariae form. Besprozvannykh et al. (2015, fig. 2) also demonstrated through 28S rRNA gene sequence data that Astiotrema species clustered away from the Plagiorchioidea and formed a monophyletic clade closer and in a basal position to the Opisthorchioidea. Thus, observations of life-cycle patterns by Besprozvannykh et al. (2015) point out a convergence between both Neoastiotrema and Astiotrema, whereas their phylogenetic results indicate a distant relationship between them. Accordingly, we conclude that: (1) reliance on life cycle patterns for differentiating between these two genera may not be useful; (2) without distinct morphological evidence, morphological data become more confusing and unconvincing for differentiating among morphologically similar taxa; hence, using molecular phylogenetic results and support may illustrate the degree of divergence or convergence and give an indicator for delimitations of species and/or higher ranks; (3) the bipartite vs unipartite nature of the seminal vesicle herein represents a stronger feature for differentiating between these two genera and it can be highly effective in differentiating at higher levels of taxonomy such as families or even superfamilies as stated by Pojmańska et al. (2008) and Tkach (2008)., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2023, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: Taxa excluded from Astiotrema (sensu stricto) with special reference to plagiorchioid genera closely related to the restricted concept of Astiotrema, pp. 445-495 in Zootaxa 5284 (3) on pages 463-464, DOI: 10.11646/zootaxa.5284.3.2, http://zenodo.org/record/7929507, {"references":["Tkach, V. V. (2008) Family Plagiorchiidae Luhe, 1901. In: Bray, R. A., Gibson, D. I. & Jones, A. (Eds.), Keys to the Trematoda. Vol. 3. CABI Publishing and the Natural History Museum, Wallingford, pp. 295 - 325. https: // doi. org / 10.1079 / 9780851995885.0295","Grabda, B. (1959 a) Astiotrema trituri sp. n. (Trematoda-Plagiorchiidae) from the small intestine of Triturus vulgaris L. Bulletin de l'Academie polonaise des Sciences. Classe II. Serie des Sciences Biologiques, 7, 17 - 21.","Grabda, B. (1959 b) The life-cycle of Astiotrema trituri B. Grabda, 1959 (Trematoda; Plagiorchiidae). Acta Parasitologica Polonica, 7, 489 - 498.","Sharpilo V. P. & Iskova N. I. (1989) Fauna of the Ukraine. Vol. 34. Trematoda. Part 3. Plagiorchiata. Naukova Dumka, Kiev, 279 pp. [in Russian]","Shevchenko, N. & Vergun, G. (1960) The life-cycle of the trematode Astiotrema monticelli Stossich, 1904. Doklady Akademii Nauk SSSR, 130, 949 - 952. [in Russian] ̕","Tkach, V. V., Pawlowski, J., Mariaux, J., Swiderski, Z., Littlewood, D. T. J. & Bray, R. A. (2001) Molecular phylogeny of the suborder Plagiorchiata and its position in the system of Digenea. In: Littlewood, D. T. J. & Bray, R. A. (Eds.), Interrelationships of the Platyhelminthes. Taylor & Francis, London, pp. 186 - 193.","Olson, P. D., Cribb, T. H., Tkach, V. V., Bray, R. A. & Littlewood, D. T. J. (2003) Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda). International Journal for Parasitology, 33, 733 - 755. https: // doi. org / 10.1016 / s 0020 - 7519 (03) 00049 - 3","Besprozvannykh, V. V., Atopkin, D. M., Ermolenko, A. V., Kharitonova, A. V. & Khamatova, A. Y. (2015) Life-cycle and genetic characterization of Astiotrema odhneri Bhalerao, 1936 sensu Cho & Seo 1977 from the Primorsky region (Russian far east). Parasitology International, 64, 533 - 539. https: // doi. org / 10.1016 / j. parint. 2015.07.008","Pojmanska, T., Tkach, V. V. & Gibson, D. I. (2008) Genera incertae sedis, genera inquirenda, nomina nuda, larval or collective names and recently erected genera. In: Bray, R. A., Gibson, D. I. & Jones, A. (Eds.), Keys to the Trematoda. Vol. 3. CABI Publishing and the Natural History Museum, Wallingford, pp. 735 - 755. https: // doi. org / 10.1079 / 9780851995885.0735"]}

The restricted concept of Astiotrema Looss, 1900 has been revised to include only eight species and various representative synonyms. However, several remaining taxa of Astiotrema (sensu lato) still need more inspection and scrutiny to determine their correct taxonomic position. Following a comprehensive review, four new genera are erected to accommodate some taxa excluded from Astiotrema (sensu stricto), three of which are closely related to this restricted concept of Astiotrema. Plesioastiotrema n. gen. is erected to accommodate Plesioastiotrema monticellii (Stossich, 1904) n. comb. (syn. Astiotrema monticellii Stossich, 1904) as the type-species and Plesioastiotrema magniovum (Fischthal & Kuntz, 1965) n. comb. (syn. Astiotrema magniovum Fischthal & Kuntz, 1965). Homeoastiotrema n. gen. is established for its type-species, Homeoastiotrema turneri (Bray, Van Oosterhout, Blais & Cable, 2006) n. comb., to accommodate Astiotrema turneri Bray, Van Oosterhout, Blais & Cable, 2006. Ichthyastiotrema n. gen. is erected with its type-species, Ichthyastiotrema fotedari (Dhar, 1977) n. comb. (syn. Astiotrema fotedari Dhar, 1977). A distinct morphologically and taxonomically distant taxon from Astiotrema (sensu stricto) is proposed in its own genus, Alloastiotrema n. gen. with its type-species, Alloastiotrema birmanii (Khan, Gul-E-Lala, Ghazi, Khatoon, Waheed & Khan, 2021) n. comb., to accommodate Astiotrema birmanii Khan, Gul-E-Lala, Ghazi, Khatoon, Waheed & Khan, 2021 and positioned distant from Astiotrema (sensu stricto). Astiotrema erinaceum (Poirier, 1886) Stossich, 1904, Astiotrema trituri Grabda, 1959 and Astiotrema (Biguetrema) tananarivense Deblock & Capron, 1962 are adopted synonyms of Galactosomum erinaceum (Poirier, 1886) Bittner & Sprehn, 1928, Neoastiotrema trituri (Grabda, 1959) Tkach, 2008 and Laiogonimus tananarivensis (Deblock & Capron, 1962) Fischthal & Thomas, 1968, respectively. Astiotrema lazeri El-Naffar, Saoud & Hassan, 1984 and Astiotrema gangeticus Gupta & Singh, 1985 nec Harshey, 1932 are synonymized with Glossidium pedatum Looss, 1899 and Orientocreadium batrachoides Tubangui, 1931, respectively. Based on its contradiction to the diagnosis of members of the Orientocreadiidae Yamaguti, 1958, we declare Orientocreadium lucknowensis Nigam, Chandra, Johri & Saxena, 2015 as incertae sedis. Longigula Qiu, Zhang & Li, 1983 and Kalipharynx Boeger & Thatcher, 1983 are morphologically closest to Astiotrema (sensu stricto) compared to members of the Plagiorchiidae Lühe, 1901 based on both genera possessing a cirrus-pouch with a unipartite, saccular seminal vesicle. The problematic status of Pseudoparamacroderoides Gupta & Agrawal, 1968 (sensu lato), the closest related genus to Astiotrema (sensu stricto), is discussed through evaluating the differential characteristics among listed species to indicate the extent of their validity and identifying the genuine species within this genus to re-evaluate the confusing and overlapping species to help understand their relationships with closely related plagiorchioids. Accordingly, only three species are recognized within Pseudoparamacroderoides Gupta & Agrawal, 1968 (sensu stricto): Pseudoparamacroderoides dongthapensis Truong, Curran & Bullard in Truong, Curran, Dutton & Bullard, 2021; Pseudoparamacroderoides pseudobagri (Wang in Wang, Zhao, Chen & Tao, 1983) n. comb. (syns. Astiotrema pseudobagri [Wang in Wang, Zhao, Chen & Tao, 1983] Karar, Blend, Dronen & Adel, 2021; Gauhatiana pseudobagri Wang in Wang, Zhao, Chen & Tao, 1983); and Pseudoparamacroderoides seenghali Gupta & Agrawal, 1968 (Syn. Pseudoparamacroderoides vittati Kakaji, 1969 n. syn.). Pseudoparamacroderoides raychaudhurii Agarwal & Kumar, 1983 is re-evaluated as Alloglossidium raychaudhurii (Agarwal & Kumar, 1983) n. comb. Anomalomacroderoiditrema n. gen. is erected for the type-species, Anomalomacroderoiditrema keni (Agarwal & Agarwal, 1984) n. comb., to accommodate specimens of Pseudoparamacroderoides keni Agarwal & Agarwal, 1984. Although the morphological convergence of Gauhatiana Gupta, 1953 within the Plagiorchioidea Lühe, 1901 has been suggested, it is neither a plagiorchiid nor a macroderoidid and does not appear closely related to Astiotrema (sensu stricto); it evidently is a member of the Monorchiidae Odhner, 1911. Alloglyptus Byrd, 1950 is taxonomically positioned as a gorgoderoid in the Allocreadiidae Looss, 1902, neither a plagiorchioid taxon nor closely related to Astiotrema (sensu stricto). The ambiguity of the seminal receptacle in some taxa of Astiotrema is discussed.

Purpose Morphological and molecular description of a new species of Haematoloechus dehradunensis sp. nov. collected from the lungs of Euphlyctis cyanophlyctis (Schneider 1799) from Dehradun (Uttarakhand), India and reporting first record of H. singaporensis from India. Methods Digeneans were fixed in AFA (alcohol-formalin-acetic acid), stained with Borax's carmine, studied and photomicrographed with a BX53 DIC/BF Olympus research microscope. Molecular studies were done by DNA isolation using Qiagen, DNeasy® Blood and Tissue Kit and PCR amplification using r-DNA ITS-1 marker situated between 18S and 1.58S gene. Results and conclusion The new species is differentiated from other known species of Haematoloechus in having larger oral sucker, kidney-shaped ovary and oval-lobed testes. H. singaporensis collected from E. cyanophlyctis represents a first record for India and a new host record. ITS sequences submitted and compared at NCBI GenBank support the uniqueness of the new species.

Astiotrema emydis Ejsmont, 1930 (Figs. 15 & 16) (Syn.: Leptophallus emydis [Ejsmont, 1930] Yeh & Fotedar, 1958) Records (see Table 1): 1. Ejsmont (1930); 2. Modrzejewska (1938). Remarks: Ejsmont (1930) proposed A. emydis for specimens from the stomach and duodenum of the European pond turtle, Emys orbicularis (Linnaeus) (Testudines: Emydidae), from Poland. Yeh & Fotedar (1958) proposed removal of A. emydis to Leptophallus Lühe, 1909; however, no reasons were given for this reassignment. Following comparison of A. emydis with two closely related species, Leptophallus nigrovenosus (Bellingham, 1844) Lühe, 1909 and Metaleptophallus gracillimus (Lühe, 1909) Yamaguti, 1958, Grabda-Kazubska (1961) concluded that the transfer of A. emydis to Leptophallus was mistaken based on the fact that A. emydis can be distinguished from species of Leptophallus by the former having a seminal receptacle and a large cirrus-pouch of a different structure without an external seminal vesicle. Grabda-Kazubska (1961) recommended that A. emydis should be retained within Astiotrema. Agrawal (1966a) concurred with Grabda-Kazubska (1961) and also noted that A. emydis could be easily distinguished from Leptophallus based on the nature of the vitellarium and the position of the cirrus-pouch. The most obvious intra-specific variation observed in this species concerns the position of the cirrus-pouch relative to the ventral sucker and ovary; it varies from either situated between ovary and ventral sucker (i.e., ventral sucker sinstral to both cirrus-pouch and ovary) (see dorsal mount of Ejsmont 1930, fig. 1) or sinistral to both ventral sucker and ovary (i.e., ventral sucker between ovary and cirrus-pouch) (see ventral mount of Modrzejewska 1938, fig. 1). Astiotrema emydis is characterized by the following diagnostic combination of morphological features: (i) oral sucker conspicuously larger than ventral sucker, (ii) vitelline fields short, extend from level midway between ventral sucker and intestinal bifurcation to level immediately posterior to posterior testis, and the anteriormost extent of vitelline fields confluent medially in pre-acetabular region, (iii) ceca long and terminate near posterior extremity or slightly anterior, (iv) ovary is either the size of testes or slightly larger and it is closer to the ventral sucker than anterior testis and (v) the esophagus of A. emydis is indistinct. Astiotrema reniferum is similar to A. emydis in its ceca extent but these species can be easily differentiated by (i) an oral sucker larger than ventral one in A. emydis vs suckers roughly equal in size in A. reniferum; (ii) A. emydis has an ovary slightly larger or equally-sized with the testes vs A. reniferum with an ovary distinctly smaller than both testis; (iii) the post-testicular area in A. emydis is larger and exceeds 2/5 of body length vs A. reniferum with a smaller area that does not exceed 1/4 of body length; (iv) A. reniferum has a distinctly long esophagus vs A. emydis with an indistinct esophagus; and (v) the vitelline field anterior to the ventral sucker is confluent in A. emydis vs not confluent in A. reniferum ., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2021, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto), pp. 36-72 in Zootaxa 4991 (1) on pages 50-52, DOI: 10.11646/zootaxa.4991.1.2, http://zenodo.org/record/5027482, {"references":["Ejsmont, L. (1930) Astiotrema emydis n. sp., ein trematode aus Emys orbicularis L. Bulletin International de l'Academie Polonaise des Sciences des Lettres, Classe des Sciences Mathematiques et Naturelles. II, Zoologie. Polska Akademia Umiejetnosci, Krakow. Wydzial Matematyczno-Przyrodniczy. Bulletin International, Krakow, Series B- 2, 2, 405 - 417.","Yeh, S. - L. & Fotedar, D. N. (1958) A review of the trematode genus Astiotrema in the Family Plagiorchiidae. Journal of Helminthology, 32, 17 - 32. https: // doi. org / 10.1017 / s 0022149 x 00019313","Modrzejewska, H. (1938) Uber die parasitischen Wurmer von Emys orbicularis aus dem Polnischen Polesie. Zoologica Polonica, 3, 125 - 139.","Luhe, M. (1909) Parasitische Plattwurmer. 1: Trematodes. Die Susswasserfauna Deutschlands, 17, 1 - 217.","Bellingham, O. B. (1844) XXII. Catalogue of Irish Entozoa, with observations. Journal of Natural History, 13, 167 - 174. https: // doi. org / 10.1080 / 03745484409442589","Yamaguti, S. (1958) Systema Helminthum. Vol. I. The Digenetic Trematodes of Vertebrates. Part 1. Interscience Publishers, Inc., New York and London, 979 pp.","Grabda-Kazubska, B. (1961) A re-description of Metaleptophallus gracillimus (Lube 1909) Yamaguti 1958 (Trematoda, Plagiorchiidae). Acta Parasitologica Polonica, 9, 101 - 107.","Agrawal, V. (1966 a) Four trematode parasites (Plagiorchiidae Luhe, 1901 emend. Ward, 1917) from reptiles of Lucknow. Revista de Biologia Tropical, 14, 133 - 151."]}

Astiotrema karachiensis Bilqees, Khatoon & Khan, 2002 n. comb. (Figs. 26 & 27) (Syn.: Astioglossimetra karachiensis Bilqees, Khatoon & Khan, 2002 n. syn.) Record (see Table 1): 1. Bilqees et al. (2002). Remarks: Astiotrema karachiensis, described by Bilqees et al. (2002) from off the Karachi coast of Pakistan as Astioglossimetra karachiensis, is easily distinguished from other species of Astiotrema as it represents the only recognized species reported from a marine host, the green sea turtle, Chelonia mydas. While we noted earlier that the green sea turtle, C. mydas, was a “suspicious habitat/name” as a host for A. hanumantharai (= A. odhneri) and in need of confirmation, herein it is considered a valid host species for A. karachiensis . Regardless of the marine environment of A. karachiensis, it is very closely related to A. odhneri in almost every morphological feature; however, some morphological differentiation should be taken into consideration to avoid overlap with A. odhneri since these particular features undergo a wide range of variation in A. odhneri . These differences include: (i) an oral sucker distinctly larger than the ventral one in A. karachiensis vs suckers roughly equal in size in A. odhneri; (ii) A. karachiensis has a conspicuous muscular esophagus vs A. odhneri which possesses a straight, longer and thinner one; and (iii) in A. karachiensis, the anterior limit of the vitelline field is at the level of the intestinal bifurcation and is thus anterior to the level of the ventral sucker, whereas in A. odhneri it is either anterior to the level of the ovary or extends further to reach the level of the anterior margin of the ventral sucker, but it does not reach the level of the intestinal bifurcation. Given the comprehensive review and newly added morphological data provided herein, we present below a key to the 8 species of Astiotrema (sensu stricto) we now recognize within this genus.

Astiotrema fotedari Dhar, 1977 (Figs. 23–25) (Syns.: Astiotrema fusiformis [Wang, 1981] n. comb.; Gauhatiana fusiformis Wang, 1981 n. syn.) Records (see Table 1): 1. Dhar (1977); 2. Wang (1981). Remarks: Dhar (1977) described A. fotedari for specimens obtained from the large intestine of the kalabans, Bangana dero (Hamilton) (Syn. Labeo dero [Hamilton]) (Cypriniformes: Cyprinidae), from Poonch in the state of Jammu and Kashmir (currently divided between India and Pakistan). Astiotrema reniferum represents the most closely related species morphologically to A. fotedari except that the former has a more restricted distribution of the vitellarium (from the level of the ventral sucker to the posterior limit of the posterior testis) and a longer esophagus while A. fotedari parasitizes a different host group (Cyprinidae) (see Dhar 1977). Wang (1981) described G. fusiformis from the intestine of the yellowfin, Xenocypris macrolepis Bleeker (Syn. Xenocypris argentea Günther) (Cypriniformes: Cyprinidae), from Fujian Province, China. We found the morphological characters of G. fusiformis to be identical to those of species of Astiotrema, while G. fusiformis differs from species of Gauhatiana particularly in lacking vitellarium in two clusters within the lateral fields and an equatorial ovary (see Gupta 1953; Wang 1981; Font & Lotz 2008); thereby, we reassign it within Astiotrema as A. fusiformis n. comb. Within a comparison with representative species of Astiotrema, we recognized that A. fusiformis has the same overall morphology and host group (Cyprinidae) as A. fotedari, though we note the slightly longer posterior extent of the cirrus-pouch relative to the posterior margin of the ovary in A. fusiformis. Consequently, A. fusiformis is herein considered a synonym of A. fotedari . Astiotrema fotedari has the following uniquely-combined features: (i) oral sucker larger than ventral one, (ii) vitelline fields long, extending anteriorly either to the level of the intestinal bifurcation or to pharyngeal level and posteriorly either to the blind ends of the ceca or slightly further posterior, (iii) ceca long, terminating a little anterior to the posterior extremity, and (iv) ovary closer to the ventral sucker than it is to anterior testis., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2021, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto), pp. 36-72 in Zootaxa 4991 (1) on page 57, DOI: 10.11646/zootaxa.4991.1.2, http://zenodo.org/record/5027482, {"references":["Dhar, R. L. (1977) Astiotrema fotedari n. sp. (Trematoda: Plagiorchidae Luhe, 1901) from the intestine of Labeo dero (Hemilton). Journal of Science, University of Kashmir, 3, 99 - 104.","Wang, P. (1981) Notes on some trematodes from freshwater fishes in Fujian Province. Fujian Shida Xuebao (Journal of the Fujian Normal University), 2, 81 - 90.","Gupta, S. P. (1953) Trematode parasites of fresh-water fishes. Indian Journal of Helminthology, 5, 1 - 80.","Font, W. F. & Lotz, J. M. (2008) Family Macroderoididae McMullen, 1937. In: Bray, R. A., Gibson, D. I. & Jones, A. (Eds.), Keys to the Trematoda, Volume 3. CABI Publishing and the Natural History Museum, Wallingford, pp. 373 - 380."]}

Astiotrema cyclemysi Siddiqi, 1965 (Figs. 21 & 22) (Syn.: Astiotrema lissemydis Agrawal, 1966 n. syn.) Records (see Table 1): 1. Siddiqi (1965); 2. Agrawal (1966a). Remarks: Siddiqi (1965) described A. cyclemysi for specimens gathered from the small intestine of the Asian leaf turtle, Cyclemys dentata (Gray) (Testudines: Geoemydidae), from Aligarh, India. Astiotrema emydis is most similar to A. cyclemysi except in the former having a maximum width at the level of the ventral sucker, possessing a larger cirrus-pouch and seminal receptacle, a submedian genital pore, oblique testes, a larger vitelline field extending from near the intestinal bifurcation and confluent medially anterior to the ventral sucker and A. emydis has much larger eggs (Ejsmont 1930; Siddiqi 1965). Agrawal (1966a) described A. lissemydis from the Indian flap-shelled turtle, Lissemys punctata (Bonnaterre) (Testudines: Trionychidae), in Lucknow, India, and distinguished it from A. emydis by the anterior extent of the vitelline fields (begins further posterior to the cecal bifurcation), ceca that extend to the posterior extremity and by having an ovary that is smaller than the testes. Astiotrema lissemydis closely resembles A. cyclemysi except that the former has vitelline follicles confluent medially in the posttesticular space, a much greater density of uterine coils, a pre-equatorial ovary and the presence of numerous glands at the base of the pharynx (Agrawal 1966a). The confluent nature of the vitelline follicles and the density of the uterine coils can both be influenced by worm maturity. Siddiqi (1965) pointed out that A. cyclemysi has an equatorial ovary in the middle third of the body but mostly situated in the anterior half of this middle third (see Siddiqi 1965, figs. 1 & 2). Astiotrema lissemydis has an ovary located in a similar position to that stated for A. cyclemysi. Given that A. cyclemysi and A. lissemydis are similar in almost all morphology (including what we believe to be slight intra-specific variation) as well as in host group (Testudines) and locality (India), A. lissemydis is herein synonymized with A. cyclemysi. We consider the following morphological features as diagnostic of A. cyclemysi: (i) oral sucker larger than ventral one, (ii) ventral sucker well-separated from the intestinal bifurcation, (iii) vitelline fields long, extend from midway between ventral sucker and intestinal bifurcation to terminate immediately posterior to level of posterior testis, (iv) ceca long, terminate near posterior extremity, (v) ovary closer to ventral sucker than anterior testis, (vi) esophagus indistinct, (vii) cirrus-pouch dorsal to ventral sucker and (viii) genital pore anterior to ventral sucker by a moderate distance, almost midway between intestinal bifurcation and the ventral sucker., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2021, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto), pp. 36-72 in Zootaxa 4991 (1) on pages 55-57, DOI: 10.11646/zootaxa.4991.1.2, http://zenodo.org/record/5027482, {"references":["Siddiqi, A. H. (1965) A new species of the genus Astiotrema Looss, 1900 with a key to its species. Journal of Helminthology, 39, 113 - 116. https: // doi. org / 10.1017 / s 0022149 x 00020101","Agrawal, V. (1966 a) Four trematode parasites (Plagiorchiidae Luhe, 1901 emend. Ward, 1917) from reptiles of Lucknow. Revista de Biologia Tropical, 14, 133 - 151.","Ejsmont, L. (1930) Astiotrema emydis n. sp., ein trematode aus Emys orbicularis L. Bulletin International de l'Academie Polonaise des Sciences des Lettres, Classe des Sciences Mathematiques et Naturelles. II, Zoologie. Polska Akademia Umiejetnosci, Krakow. Wydzial Matematyczno-Przyrodniczy. Bulletin International, Krakow, Series B- 2, 2, 405 - 417."]}

Type-species: Astiotrema reniferum (Looss, 1898) Looss, 1900 Diagnosis. Body large, elongate to elongate oval, spatulate. Tegument spinous. Forebody approximately one third of total body length. Suckers subglobular, unspecialized, with variable sucker ratio. Oral sucker subterminal. Ventral sucker in anterior third of body or at border between anterior and middle thirds. Prepharynx indistinct to absent. Pharynx well developed, smaller than suckers. Esophagus of varying length to indistinct, straight to sigmoid. Intestine bifurcates in posterior or anterior part of forebody. Cecal ends variable in extent, close to posterior extremity or some distance short of it in middle third of body. Testes two, intercecal, smooth to indented, separated by small inter-testicular space, elliptical to slightly irregular, tandem to oblique, rarely opposite. Cirrus-pouch clavate, submedian or diagonal to midline, extends distinctly into hindbody. Internal seminal vesicle large, thick-walled, saccular to elongate saccular, unipartite, occasionally slightly sinuous; pars prostatica and ejaculatory duct short, tubular, inconspicuous. Genital atrium short, inconspicuous. Genital pore immediately anterior to ventral sucker, postbifurcal to occasionally bifurcal, median to slightly submedian. Ovary globular to elliptical, intercecal, pre-equatorial, dextral to dextro-submedian, entire, at base of cirrus-pouch or lateral to it. Canalicular seminal receptacle distinct, post-ovarian, variable in size, elliptical to kidney-shaped. Vitellarium follicular, in extracecal fields and sometimes extends dorsal and ventral to ceca, extends longitudinally between pharynx and cecal extremities; anterior extent pre-bifurcal, bifurcal or post-bifurcal; posterior extent pre-testicular, testicular or post-testicular. Uterus inter- and post-cecal, occasionally slightly extracecal, fills inter-testicular space and most of hindbody posterior to ovary, extends to posterior extremity. Metraterm simple, originates alongside cirrus-pouch. Eggs operculated, elliptical, unfilamented, tanned, unembryonated in utero, numerous. Excretory vesicle Y-shaped; stem passes between testes and bifurcates in two short arms between ovary and anterior testis. Excretory pore terminal. In intestine of various freshwater fishes (Bagridae, Cichlidae, Clariidae, Cyprinidae, Heteropneustidae & Tetraodontidae), amphibians (Bufonidae, Dicroglossidae & Hylidae), lizards (Varanidae) and turtles (Cheloniidae, Emydidae, Geoemydidae & Trionychidae); cosmopolitan in Asia, Europe and Africa. Remarks: Looss (1896) erected Distoma unicum Looss, 1896 for specimens collected from the intestine of the African or Nile soft-shelled turtle, Trionyx triunguis (Forsskål) (Syn. Trionyx niloticus Gray) (Testudines: Trionychidae), in the River Nile of Egypt. Due to the homonym observed with Distomum unicum Molin, 1859 (see Molin 1859), Looss (1898) renamed his specimens Distomum reniferum Looss, 1898. A year later, Looss (1899) considered D. reniferum as the type species of Astia Looss, 1899. As Astia Koch, 1879 was already preoccupied (i.e., an arachnid genus for Australian jumping spiders—see Koch [1879]), Looss (1900) changed Astia to Astiotrema Looss, 1900 with type species, Astiotrema reniferum. Tremiorchis Mehra & Negi, 1926 was erected for the type-species Tremiorchis ranarum Mehra & Negi, 1926 collected from the small intestine and duodenum of the Indian bullfrog, Hoplobatrachus tigerinus (Daudin) (Syn. Rana tigrina [Duadin]) (Anura: Dicroglossidae), in Northern India (Mehra & Negi 1926). That same year, from the intestine of the same host, H. tigerinus, from Allahabad and Nagpur, India, Bhalerao (1926) proposed Centrovitus Bhalerao, 1926 for its type species Centrovitus pentadelphi Bhalerao, 1926. Ejsmont (1928) presented a detailed comparison between T. ranarum and C. pentadelphi and, consequently, C. pentadelphi was synonymized with T. ranarum, and it followed that Centrovitus was considered a synonym of Tremiorchis. Verma (1930) supported the conclusions of Ejsmont (1928), discussed the systematic position of Tremiorchis, modified the generic diagnosis of Tremiorchis based on describing another species, Tremiorchis varanum Verma, 1930, and revised its taxonomic position clarifying the high importance of Tremiorchis because of possessing common features with several genera of the Plagiorchiinae Pratt, 1902 (= Plagiorchiidae Lühe, 1901) and probably some genera of the Brachycoeliinae Looss, 1899 (currently considered a synonym of the Brachycoeliidae Looss, 1899). Mehra (1931a) transferred Tremiorchis to the Lepodermatinae Looss, 1899 from the Lepodermatidae Looss, 1899. Thus far, most of the dispute involving the taxonomic status of Tremiorchis has involved whether this genus belongs to the Plagiorchiidae (Bhalerao 1926; Mehra & Negi 1926; Mehra 1931a; Bhardwaj 1962; Rai 1962; Gupta, 1964; Skrjabin et al. 1964; Agrawal 1968; Ali & Karyakarte 1970; Mukherjee & Ghosh 1972; Singh 1977; Hafeezullah 1989; Rajendran & Janardanan 1993; Bhutia 2006; Pandey & Agrawal 2013) or the Brachycoeliidae (Dollfus 1930; Kalyanker & Palladwar 1978; Hafeezulla & Dutta 1981; Ghosh & Chakraborty 1999; Ghosh & Srivastava 1999; Bilqees & Khan 2003; Pojmańska 2008; Ghosh & Chakrabarti 2013; Keloth & Kandambeth 2018). Bhardwaj (1962) erected the Tremiorchinae Bhardwaj, 1962 within the Plagiorchiidae to accommodate Tremiorchis based on (i) the plagiorchiid nature of Tremiorchis despite its considerable divergence from this line of evolution, (ii) the convergence of Tremiorchis with the Dicrocoeliidae Odhner, 1910 in regard to the shortening of the ceca and the limited extent and size of the vitellarium, (iii) the potential evolution of Brachycoelium Dujardin, 1845 from Tremiorchis reflected in maintaining the Brachycoelinae Looss, 1899 within the Plagiorchiidae (see Mehra 1931a), and (iv) the assignment of the Brachycoelinae among the dicrocoeliids. Fotedar (1971) compared the generic characteristics of Tremiorchis with Astiotrema, synonymized both genera, and considered T. ranarum as Astiotrema ranarum (Mehra & Negi, 1926) Fotedar, 1971. Rajendran & Janardanan (1993) apparently did not recognize the synonymy of Tremiorchis with Astiotrema and presented a detailed life-cycle of T. ranarum revealing that the first intermediate host was the amphibious apple snail, Pila virens (Lamarck) (Gastropoda: Ampullariidae), and that the second intermediate hosts were tadpoles of the Indian bullfrog, H. tigerinus, and the Indian skittering frog, Euphlyctis cyanophlyctis (Schneider) (Syn. Rana cyanophlyctis [Schneider]) (Anura: Dicroglossidae), which within the former sporocysts produce xiphidiocercariae. Pojmańska (2008) and Pojmańska et al. (2008) considered Tremiorchis and Astiotrema separate genera; Pojmańska et al. (2008) concluded Astiotrema a genus incertae sedis in the Plagiorchioidea (sensu lato) Pojmańska, 2008 whilst Pojmańska (2008) reassigned Tremiorchis to the Brachycoeliidae, distinguishing it from other brachycoeliids by an elongate body, ceca that terminate anterior to or in the testicular zone, ceca and vitellarium that reach to the level of the testis, and a large distance between the ovary and testes. In addition, T. ranarum and T. varanum were considered as members of Tremiorchis (Pojmańska 2008, figs 12.1, 12.2). Besprozvannykh et al. (2015) established a genetic characterization and a detailed description of a life-cycle for Astiotrema odhneri Bhalerao, 1936 as well as discussed previously reported life-cycles for species of Astiotrema. This revealed some points of high phylogenetic and ontogenetic importance: (i) the first intermediate host of A. odhneri is a planorbid snail, Anisus (Gyraulus) centrifugops Prozorova & Starobogatov (Gastropoda: Planorbidae), while the second intermediate hosts include the ramhorn snail, Helicorbis sujfunensis Starobogatov (Gastropoda: Planorbidae), and A. centrifugops, tadpoles of the Dybowski’s frog, Rana dybowskii Günther (Anura: Ranidae), and the Chinese sleeper fish, Perccottus glenii Dybowski (Perciformes: Odontobutidae); (ii) sporocysts develop in xiphidiocercariae; and (iii) A. odhneri clustered with other 28S rRNA gene sequences of Astiotrema forming a monophyletic clade closer and in a basal position to the Opisthorchioidea, obviously distant and separated from all members of the Plagiorchioidea. Furthermore, Besprozvannykh et al. (2015) disagreed with Shevchenko & Vergun (1960) regarding the interpretation of the life-cycle of Astiotrema monticellii Stossich, 1904; the analysis by Besprozvannykh et al. (2015) indicated that Shevchenko & Vergun (1960) most likely described larvae belonging to a member of the Opisthorchioidea rather than a species of Astiotrema. Thus, in their view, the prosobranch (gilled) snail Bithynia leachii (Sheppard) (Gastropoda: Bithyniidae) did not represent a first intermediate host for A. monticellii and the development of this parasite includes neither formation of rediae nor cercariae from the Pleurolophocerca group. Regarding the criteria and diagnostic features of Tremiorchis proposed by Pojmańska (2008) (see above), we conclude that these characters are identical with published diagnoses of Astiotrema (sensu stricto); therefore, we do not support placing Tremiorchis within the Brachycoeliidae. Based on the similarities between Tremiorchis and Astiotrema (sensu stricto), particularly in morphology and life history (i.e., observed intermediate hosts and development of a xiphidiocercaria within a sporocyst), we again consider Tremiorchis a synonym of Astiotrema (sensu stricto), consequently validating A. ranarum within Astiotrema (sensu stricto). Bilqees et al. (2002) created Astioglossimetra for its type species Astioglossimetra karachiensis Bilqees, Khatoon & Khan, 2002, collected from the intestine of the green sea turtle, Chelonia mydas (Linnaeus) (Testudines: Cheloniidae), off the coast of Karachi, Pakistan. Bilqees et al. (2002) differentiated Astioglossimetra from two closely related genera, Astiotrema and Glossimetra Mehra, 1937, based on the shorter length of the vitelline fields and ceca in the former. Pojmańska et al. (2008) discussed the status of Astioglossimetra and pointed out its resemblance to members of both Astiotrema and Neoastiotrema Tkach, 2008; however, the problematic taxonomic status of Astioglossimetra resulted in it being declared temporarily a genus incertae sedis based on the fact that (i) both Astiotrema and Neoastiotrema are known only from freshwater habitats and hosts (Astioglossimetra was reported from a marine turtle in the northern Arabian Sea), and (ii) the description of the seminal vesicle in A. karachiensis as “smooth or bipartite” is ambiguous in that it may potentially put this genus into two families or even superfamilies. Bilqees et al. (2002) described A. karachiensis based on three specimens from a single host, two of which were fully illustrated with their genital systems in addition to the genital system only of the third specimen (see Bilqees et al. 2002, figs. 1–3). The seminal vesicle in the holotype and one paratype is unipartite (see Bilqees et al. 2002, figs. 1 & 3); whereas, this feature appears to have a slightly sinuous wall (i.e., a somewhat “pinched” appearance) but not a distinct constriction dividing the seminal vesicle into two parts that is more indicative of a bipartite structure in the third figure (see Bilqees et al. 2002, fig. 2). There have been similar cases observed in other species of Astiotrema (see Mehra 1931b, fig. 2; Bhalerao 1936, fig. 4; Tang 1941, fig. 19; Gupta 1954, fig. 5; Dollfus & Simha 1964, fig. 1; Wang 1987, fig. 2) strongly indicating that the seminal vesicle in Astioglossimetra is unipartite. In addition, it has been our experience that the seminal vesicle of many flukes develops by the spiraling or twisting of a more tubular singular structure, where depending on the number of resultant twists, there may be a main chamber (unipartite), two main chambers (bipartite) or three main chambers (tripartite). This development may confuse the issue of its actual structure based on the age of the specimens and how far along the development of this feature may be. The illustrated holotype (Bilqees et al. 2002, fig. 1) appears to be an early mature specimen whereas the illustrated paratype (fig. 3) represents a fully gravid specimen and both have a unipartite seminal vesicle, thus, the unipartite structure of the seminal vesicle in Astioglossimetra is confirmed. Accordingly, Astioglossimetra appears more closely related to Astiotrema than Neoastiotrema (i.e., unipartite seminal vesicle in the former vs a bipartite one in the latter). As for the recording of Astioglossimetra from the marine turtle C. mydas and in contrast to records of Astiotrema from freshwater habitats and hosts, C. mydas has been known to enter rivers and feed for reasonably long periods of time (Cammarata & Dronen 2020); consequently, potential infection of C. mydas with a species of Astiotrema is possible. Furthermore, C. mydas belongs to a large, widely distributed and variant group, the Testudines, which represent one of the most common hosts for species of Astiotrema (see Discussion below); therefore, we cannot exclude the presence of marine species of Astiotrema in marine turtles. Bilqees et al. (2002) stated that Astioglossimetra is characterized by having a relatively short longitudinal distribution of the vitellarium from the intestinal bifurcation to a level anterior to the posterior testis and by having short ceca that terminate anterior to or at the level of the posterior testis. Our research clarified that species of Astiotrema exhibit a wide spectrum in the vitelline field length (between pharynx and cecal extremities) and in the location of the cecal ends (from level of anterior testis to near posterior extremity). Thus, the criteria used by Bilqees et al. (2002) for differentiating Astioglossimetra fall within those of Astiotrema and appear to be effective for differentiating species, but not at the generic level. Based on the identical morphology, the sharing of the same host group (Testudines), and the closely related localities (Pakistan & India) reported between Astioglossimetra and Astiotrema, we hereby consider Astioglossimetra to be another synonym of Astiotrema. Pojmańska et al. (2008) included some vague and problematic genera within the Plagiorchioidea (sensu lato) as genera incertae sedis. As stated earlier, the ambiguous state of Astiotrema is attributed to its closer phylogenetic affinity to opisthorchioids and their positioning together in one cluster distinctly separated from plagiorchioids (see Tkach et al. 2001; Olson et al. 2003; Pojmańska et al. 2008; Tkach 2008; Besprozvannykh et al. 2015; de León & Hernández-Mena 2019) despite Astiotrema resembling the latter in its morphology and life-cycle patterns (see Pojmańska et al. 2008; Tkach 2008; Besprozvannykh et al. 2015). For interpreting the ambiguous phylogenetic status of Astiotrema, Tkach et al. (2001) suggested two variants: either Astiotrema is unrelated to the Plagiorchiidae or it represents a heterogeneous group with polyphyletic origin where some of its members may belong not only to different genera, but even to different families; Galaktionov & Dobrovolskij (2003) adopted the latter variant. Pojmańska et al. (2008) considered Astiotrema as incertae sedis within the Plagiorchioidea (sensu lato). Besprozvannykh et al. (2015) revealed through molecular studies that Astiotrema is phylogenetically closer to opisthorchioids and separate from plagiorchioids (as stated earlier by Pojmańska et al. 2008); however, they considered Astiotrema as incertae sedis within the Opisthorchioidea. Due to the potential polyphyletic origin of Astiotrema and its closely resembling the Plagiorchioidea in morphology and life-cycle patterns, we prefer to consider this genus within the expanded concept of the Plagiorchioidea (Pojmańska et al. 2008) until such a time as the actual systematic position of Astiotrema can be determined., Published as part of Karar, Yasser F. 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Astiotrema odhneri Bhalerao, 1936 (Figs. 17–20) (Syns.: Astiotrema reniferum of Odhner, 1911 nec Looss, 1898; Astiotrema orientale Yamaguti, 1937; Astiotrema amydae Ogawa, 1938; Astiotrema fukuii Ogawa, 1938; Astiotrema foochowensis Tang, 1941; Astiotrema matthaii Gupta, 1954; Astiotrema nathi Gupta, 1954; Astiotrema srivastavai Gupta, 1954; Astiotrema geomydia Siddiqui, 1958 n. syn.; Astiotrema mehrai Tiwari, 1958; Astiotrema sudanensis Khalil, 1959 n. syn.; Astiotrema cirricurvatus Simha & Chattopadhyaya, 1971 n. syn.; Astiotrema brevicaecum Wang, 1987 n. syn.; Astiotrema hanumantharai Dhanumkumari, 1999 n. syn.) Records (see Table 1): 1. Odhner (1911); 2. Bhalerao (1936); 3. Yamaguti (1937); 4. Ogawa (1938); 5. Tang (1941); 6. Gupta (1954); 7. Siddiqui (1958); 8. Tiwari (1958); 9. Yeh & Fotedar (1958); 10. Khalil (1959); 11. Ahluwalia (1960); 12. Dollfus & Simha (1964); 13. Agrawal (1966a); 14. Fotedar (1971); 15. Simha & Chattopadhyaya (1971); 16. Cho & Seo (1977); 17. Wang (1987); 18. Dhanumkumari (1999); 19. Besprozvannykh et al. (2015). Remarks: Odhner (1911) identified specimens of Astiotrema collected from the intestine of the African or Nile softshell turtle, T. triunguis (Testudines: Trionychidae), as A. reniferum. Bhalerao (1936) discussed the specimens of Odhner (1911) and disputed their identity as A. reniferum . This was based on these specimens having (i) shorter ceca terminating at the posterior limit of the posterior testis level, (ii) lobed and differently-shaped testes, (iii) an ovary positioned more anteriorly in the anterior third of the body and (iv) vitellarium distributed differently when compared with the first description of A. reniferum (as Distomum reniferum) by Looss (1898) and its updates (Looss 1899, 1900). Therefore, A. odhneri was proposed by Bhalerao (1936) for the specimens of Odhner (1911). Yeh & Fotedar (1958) presented a major revision of 21 species of Astiotrema in which they recognized A. odhneri, synonymized 8 species with it and explained the importance of ceca length as a taxonomic character in Astiotrema. Khalil (1959) synonymized A. odhneri with A. reniferum based on (i) the variability in the length of ceca (i.e., terminations of ceca range from near the posterior extremity to the posterior margin of the posterior testis) in specimens collected from the Sudan from the type host of A. odhneri and (ii) the nonspecific importance of testis shape and lobulation as explained by Yeh & Fotedar (1958). Fotedar (1971) disagreed with the action by Khalil (1959); pointing out the consistent difference in cecal length between the two species as well as the possibility that Khalil (1959) had dealt with two different species of Astiotrema from the same host. At present, the taxonomic status of A. odhneri relative to A. reniferum remains disputed; some authors have accepted their conspecificity (see Khalil 1959; Dollfus & Simha 1964; Siddiqi 1965; Agrawal 1966a; Simha & Chattopadhyaya 1971; El-Naffer et al. 1984; Gupta & Saxena 1987) and others have not (see Yeh & Fotedar 1958; Cho & Seo 1977; Dhar 1977; Besprozvannykh et al. 2015). Through a detailed review focusing on A. odhneri and A. reniferum, their synonyms and closely related congeners, we found (i) no report, record, comment, description or illustration documenting a noticeably wide variation in the posterior extent of the ceca for a species of Astiotrema; (ii) the original description of A. reniferum (see Looss 1899) and the revisions by Yeh & Fotedar (1958) and Kumari et al. (1972) clarified that the ceca of A. reniferum terminate either a little anterior to the posterior extremity or midway between the posterior testis and posterior extremity; (iii) based on the specimens of Odhner (1911), subsequent studies of A. odhneri (Cho & Seo 1977; Besprozvannykh et al. 2015) and the corresponding synonyms for this species made by Yeh & Fotedar (1958), we clarify that in A. odhneri the ceca reliably terminate at the posterior border of the posterior testis; (iv) considering the total change in the posterior extent of the ceca from the level of the posterior extent of the posterior testis to the posterior extremity of the body as a predictable slight variation, this causes overlap among several species of Astiotrema, thus, complicating the taxonomic status of this digenean genus more than it is now. Accordingly, we concur with Yeh & Fotedar (1958) and Fotedar (1971) and consider A. odhneri a species separated from A. reniferum and we support the opinion of Fotedar (1971) that Khalil (1959) dealt with two species of Astiotrema from the same host; the same case observed later by Cho & Seo (1977) who redescribed both A. reniferum and A. odhneri from the intestine of the same host (the Chinese soft-shelled turtle, Pelodiscus sinensis Wiegmann [Syn. Amyda sinensis Stejneger] [Testudines: Trionychidae], from South Korea). Variation reported in some morphological features of A. odhneri is similar to that observed for A. reniferum: (i) size of oral sucker either slightly larger or smaller than ventral one or suckers equally-sized; (ii) seminal receptacle can vary in shape and size; (iii) posterior extent of cirrus-pouch ranges from a slight distance anterior to ovary to slightly posterior to it; (iv) testes shape and position vary from globular to oval to irregular and from oblique to obliquely tandem; (v) ceca terminate in range from anterior to posterior margins of posterior testis; (vi) spines on tegument extend from anterior extremity to either the anterior limit of last 1/3 of body or to posterior extremity; and (vii) vitelline field distribution, extending either from anterior to ovarian level or level of anterior margin of ventral sucker to either level of anterior margin of posterior testis or posterior margin of it. We think that these variations are neither diagnostic for differentiating species nor cast doubt on conspecificity with A. odhneri. Thus, we concur with Yeh & Fotedar (1958) and consider A. amydae, A. foochowensis, A. fukuii, A. matthaii , A. nathi, A. orientale and A. srivastavai synonyms of A. odhneri . Siddiqui (1958) described A. geomydia from the intestine of the spiny turtle, Heosemys spinosa (Gray) (Syn. Geomyda spinosa Gray) (Testudines: Geoemydidae), from Aligarh, India, and noted the close resemblance of his specimens with those of A. rami (= A. reniferum —see above), yet recognized both species. Ahluwalia (1960) and Fotedar (1971) considered A. geomydia a synonym of A. impletum . In the current study, A. geomydia is differentiated from A. reniferum by its large post-testicular region and ceca that end near the level of the posterior testis; A. geomydia is differentiated from A. impletum by the shorter anterior extent of its vitellarium (i.e., entirely post-acetabular and extends to level of cirrus-pouch) and ovary being closer to the anterior testis than the ventral sucker. Consequently, we find that A. geomydia neither resembles A. reniferum nor A. impletum and we consider it another synonym of A. odhneri based on its identical morphology and consistent nature of the habits and habitats of the host species (i.e., Testudines). Tiwari (1958) described A. mehrai from the intestine of the three-striped or dhond roofed turtle, B. dhongoka (Testudines: Geoemydidae), from Raipur, India. Astiotrema mehrai exhibited a close relation with A. reniferum (Syns. A. dassia, A. indica and A. thapari) based on having equally sized suckers but differed by its possession of rounded testes, shorter ceca and in the distribution of vitelline follicles. Dollfus & Simha (1964) identified specimens of A. reniferum from the intestine of the red-crowned or painted roofed turtle, Batagur kachuga (Gray) (Syn. Kachuga kachuga Smith) (Testudines: Geoemydidae), from Hyderabad, India; this identification was found to be unjustified and the true species should be A. odhneri based on the ceca terminating at the anterior limit of the posterior testis level as well as the presence of a large post-cecal area. Agrawal (1966a) and Simha & Chattopadhyaya (1971) indicated the high spectrum apparent in regard to shape of testes, length of ceca and vitellarium extent, thereby they synonymized A. mehrai with A. reniferum and Gupta & Singh (1985) followed this synonymy; however, A. mehrai differs from A. reniferum by the former possessing ceca that end at the level of the posterior testis and a longer post-cecal area, features typically characteristic of A. odhneri . Due to additional similarities between A. mehrai and A. odhneri (i.e., known geographical distribution [India] for A. odhneri, main host group [Testudines] and morphological variation), we support the view of Fotedar (1971) that A. mehrai is a synonym of A. odhneri. Khalil (1959) added A. sudanensis from the intestine of the African or Nile softshell turtle, T. triunguis (Testudines: Trionychidae), from Sudan and pointed out its resemblance to A. reniferum, but noted that it differed in the relative sizes of the two suckers, the extent of the vitellarium and the smaller size of the eggs. Agrawal (1966a) considered A. sudanensis a synonym of A. reniferum, while Fotedar (1971) cast doubt on the validity of A. sudanensis, clarified its close relationship with A. impletum, and pointed out the necessity of re-examining the specimens of Khalil (1959) to determine the validity of A. sudanensis. Focusing on the type description of A. sudanensis , we did not find any differences between A. sudanensis and A. odhneri . Both species have the same morphology, reported host group (Trionychidae) and type host, T. triunguis . Accordingly, we consider A. sudanensis a synonym of A. odhneri . Astiotrema cirricurvatus was recorded from the intestine of the Nagpur soft-shelled turtle, Nilssonia leithii (Gray) (Syn. Trionyx leithi Alderton) (Testudines: Trionychidae), found in the Manjara (= Manjira) River, Karnataka (previously Mysore) State, India (Simha & Chattopadhyaya 1971). They differentiated A. cirricurvatus from all other congeneric species by its larger cirrus-pouch, the terminal portion of which curves around the posterior and right lateral border of the ventral sucker. We have observed that several species of Astiotrema have a large cirrus-pouch (see Siddiqui 1958; Wang 1987; Dhanumkumari 1999) while others have a cirrus-pouch of varying sizes. It is also possible that the size of the cirrus-pouch may be influenced by the volume of spermatozoa within it. Concerning the curvature of the terminal portion of the cirrus-pouch (ejaculatory duct) around the posterior and right lateral border of the ventral sucker, this character is present in several species of Astiotrema (see Fischthal & Kuntz 1965; Dhanumkumari 1999; A. impletum from present study). Consequently, we do not think that the size and course of the cirrus-pouch, as the purported characters used by Simha & Chattopadhyaya (1971) for differentiating A. cirricurvatus, are valid, and we consider A. cirricurvatus a synonym of A. odhneri based on their morphological and ecological similarity (i.e., hosts belong to the Trionychidae Fitzinger). Wang (1987) described A. brevicaecum from two specimens obtained from the intestine of the Chinese softshelled turtle, Pelodiscus sinensis (Syn. Trionyx sinensis Strauch) (Testudines: Trionychidae), collected in Taining County, Fujian Province, China, and clarified its close relation with A. monticellii. The present study revealed that A. brevicaecum has the same morphological characteristics of A. odhneri as well as the same host family (Trionychidae) and is from a previously well-known geographical locality (Asia) for A. odhneri (Syn. A. foochowensis) (see Tang 1941; Wang 1987). Accordingly, we synonymize A. brevicaecum with A. odhneri. Dhanumkumari (1999, p. 204) proposed A. hanumantharai for specimens collected from the intestine of two distinctly separate hosts: a freshwater host, the stinging catfish, Heteropneustes fossilis (Bloch) (Siluriformes: Heteropneustidae), and a turtle of either a suspicious habitat (i.e., “freshwater”) or a suspicious name (i.e., “ Chelone mydas ” Boulenger [Testudines: Cheloniidae]), the green sea turtle, both “from in and around” Visakhapatnam, Andhra Pradesh, India. Astiotrema hanumantharai exhibits a close relationship morphologically with A. reniferum and its synonyms, A. manteri and A. kachugai, as well as a great resemblance to A. odhneri (see Simha & Chattopadhyaya 1971; Syn. A. cirricurvatus) with just a minor difference that A. hanumantharai has a smaller cirrus-pouch; we thereby conclude A. hanumantharai as a synonym of A. odhneri. The finding by Dhanumkumari (1999) of A. odhneri is the first time this species has been recorded from a freshwater fish. Regarding the suspicious habitat of the reported turtle, Dhanumkumari (1999) stated that Chelonia mydas (Linnaeus) (Syn. Chelone mydas) (Testudines: Cheloniidae) was another host for his specimens despite the fact that C. mydas is distinctly a marine species commonly known as the green sea turtle, green turtle, black sea turtle or Pacific green turtle (Uetz et al. 2021). Although it does feed at times in freshwater habitats (see Cammarata & Dronen 2020), we suspect that Dhanumkumari (1999) may have been mistaken in determining the exact habitat of C. mydas to be marine, not freshwater. Assuming that the habitat sampled was freshwater, we suspect that Dhanumkumari (1999) may have been mistaken in the identification of the turtle host based on the fact that Visakhapatnam is a city rich in tortoises and freshwater turtles as well as marine ones, and previously recorded hosts of Astiotrema have been limited to freshwater or terrestrial habitats. Accordingly, confirmation is needed for the turtle species sampled., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2021, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto), pp. 36-72 in Zootaxa 4991 (1) on pages 52-55, DOI: 10.11646/zootaxa.4991.1.2, http://zenodo.org/record/5027482, {"references":["Bhalerao, G. D. (1936) Studies on the helminths of India. Trematoda II. Journal of Helminthology, 14, 181 - 206. https: // doi. org / 10.1017 / s 0022149 x 00004089","Odhner, T. (1911) Nordostafrikanische Trematoden, grosstenteils vom Weissen Nil. I. Fascioliden. Results of the Swedish Zoological Expedition to Egypt and the White Nile (1901), 23, 1 - 170.","Looss, A. (1898) Quelques observations a propos de la note: Forme nouve etc. de entozoi d'Egitto de Mr le docteur Sonsino dans Ce Journal. 1896. Centralblatt fur Bakteriologie, Parasitenkunde und Infektionskrankheiten, 23, 453 - 461.","Yamaguti, S. (1937) Studies on the helminth fauna of Japan. Part 18. Two species of trematodes from the intestine of a tortoise, Amyda japonica (Tem et Schleg.). Published by the author, Kyoto, 4 pp.","Ogawa, T. (1938) Note preliminaire sur deux especes nouvelles de trematodes du genre Astiotrema, provenant de l' Amyda maackii. Zoological Magazine, 50, 50 - 52.","Tang, C. C. (1941) Contribution to the knowledge of the helminth fauna of Fukien. Part I. Avian, reptilian and mammalian trematodes. Peking Natural History Bulletin, 15, 299 - 316.","Gupta, N. K. (1954) On five new trematodes of the genus Astiotrema Looss, 1900, from the intestine of Lissemys punctata punctata and discussion on the synonymity of two already known forms. Research Bulletin of the Panjab University, 49 / 50, 85 - 100.","Siddiqui, W. A. (1958) On a new trematode, Astiotrema geomydia (Family Plagiorchidae), from an Indian tortoise. Zeitschrift fur Parasitenkunde, 18, 219 - 222. https: // doi. org / 10.1007 / bf 00259194","Tiwari, I. P. (1958) Studies on three new species of the genus Astiotrema (Trematoda: Plagiorchiidae) from fresh water tortoises. Proceedings of the National Academy of Sciences of India, Section B. Biological Sciences, 28, 246 - 252.","Khalil, L. F. (1959) On a new trematode, Astiotrema sudanensis, sp. nov., from a freshwater turtle in the Sudan. Journal of Helminthology, 33, 263 - 266. https: // doi. org / 10.1017 / s 0022149 x 00020149","Simha, S. S. & Chattopadhyaya, D. R. (1971) On a new species of the genus Astiotrema Looss, 1900 from the intestine of a fresh water turtle, Trionyx leithi, from Gulburga, Mysore State, India. Rivista di Parassitologia, 32, 21 - 25.","Wang, P. (1987) Four new species of digenetic trematodes from the amphibians and reptiles of Fujian. Acta Herpetologica Sinica, 6, 67 - 70.","Dhanumkumari, C. (1999) On a new species of the genus Astiotrema Looss, 1900 from the intestines of Heteropneustes fossius and Chelone mydas from Visakhapatnam India. Rivista di Parassitologia, 60, 203 - 207.","Yeh, S. - L. & Fotedar, D. N. (1958) A review of the trematode genus Astiotrema in the Family Plagiorchiidae. Journal of Helminthology, 32, 17 - 32. https: // doi. org / 10.1017 / s 0022149 x 00019313","Ahluwalia, S. S. (1960) On two genera of trematode parasites of a fresh-water tortoise. Proceedings of the 47 th Indian Science Congress, 3, 437. [abstract]","Dollfus, R. - P. & Simha, S. S. (1964) Speciation d'un distome du genere Astiotrema A. Looss, 1900 d'un Chelonien de lnde. Bulletin du Museum d'Histoire Naturelle, 36, 262 - 267.","Agrawal, V. (1966 a) Four trematode parasites (Plagiorchiidae Luhe, 1901 emend. Ward, 1917) from reptiles of Lucknow. Revista de Biologia Tropical, 14, 133 - 151.","Fotedar, D. N. (1971) On the synonymy of the trematode genera Astiotrema Looss, 1900 and Tremiorchis Mehra and Negi, 1925, and notes on the existing species of the genus. Journal of Parasitology, 57, 39 - 40.","Cho, S. Y. & Seo, B. S. (1977) Studies on the parasitic helminths of Korea IV. Intestinal trematodes from freshwater mud-turtle (Amyda sinensis Wiegmann) with description of new species, Cotylaspis coreensis. The Korean Journal of Parasitology, 15, 1 - 10. https: // doi. org / 10.3347 / kjp. 1977.15.1.1","Besprozvannykh, V. V., Atopkin, D. M., Ermolenko, A. V., Kharitonova, A. V. & Khamatova, A. Y. (2015) Life-cycle and genetic characterization of Astiotrema odhneri Bhalerao, 1936 sensu Cho & Seo 1977 from the Primorsky region (Russian far east). Parasitology International, 64, 533 - 539. https: // doi. org / 10.1016 / j. parint. 2015.07.008","Looss, A. (1899) Weitere Beitrage zur Kenntnis der Trematodenfauna Aegyptens, zugleich Versuch einer naturlichen Gliederung des Genus Distomum Retzius. Zoologische Jahrbucher, 12, 521 - 784. https: // doi. org / 10.5962 / bhl. part. 2037","Looss, A. (1900) Nachtragliche Bemerkungen zu den Namen der von mir vorgeschlagenen Distomidengattungen. Zoologischer Anzeiger, 23, 601 - 608.","Siddiqi, A. H. (1965) A new species of the genus Astiotrema Looss, 1900 with a key to its species. Journal of Helminthology, 39, 113 - 116. https: // doi. org / 10.1017 / s 0022149 x 00020101","Gupta, V. & Saxena A. M. (1987) On a new trematode Astiotrema manteri sp. nova from Kachuga intermedia (Boulenger) from Lucknow and a review of the genus Astiotrema (Looss, 1898) Looss, 1900. Indian Journal of Helminthology, 39, 114 - 122.","Dhar, R. L. (1977) Astiotrema fotedari n. sp. (Trematoda: Plagiorchidae Luhe, 1901) from the intestine of Labeo dero (Hemilton). Journal of Science, University of Kashmir, 3, 99 - 104.","Kumari, N. V., Srivastava, C. B. & Chauhan, B. S. (1972) Redescription of Astiotrema reniferum (Looss, 1898) Looss, 1900 with comments on the status of the genus Pseudoparamacroderoides Gupta & Agarwal, 1968 (Trematoda: Plagiorchiidae). Records of the Zoological Survey of India, 67, 315 - 323.","Gupta, P. C. & Singh, R. (1985) Two new species of digenetic trematodes of fishes in India. Pakistan Journal of Zoology, 17, 329 - 334.","Fischthal, J. H. & Kuntz, R. E. (1965) Digenetic trematodes of amphibians and reptiles from North Borneo (Malaysia.). Proceedings of the Helminthological Society of Washington, 32, 124 - 136.","Uetz, P., Freed, P. & Hosek, J. (Eds.) (2021) The Reptile Database. Available from: http: // www. reptile-database. org (accessed 20 April 2021)","Cammarata, C. A. & Dronen, N. O. (2020) Two new species of Telorchis (Digenea: Telorchiidae) from a green turtle, Chelonia mydas (Cheloniidae), stranded along the upper Texas coast. Journal of Parasitology, 106, 755 - 771. https: // doi. org / 10.1645 / 20 - 27"]}

Key to species of Astiotrema Looss, 1900 (sensu stricto) 1a. Cecal ends either not reaching significantly into or do not exceed testicular zone.................................. 2. 1b. Cecal ends extending deeply into post-testicular zone....................................................... 5. 2a. Cecal ends and posterior vitellarium extent exceed level of anterior testis; parasitize non-amphibian hosts.............. 3. 2b. Cecal ends and posterior vitellarium extent do not exceed level of anterior testis; parasitize amphibian hosts........................................................ Astiotrema ranarum (Mehra & Negi, 1926) Fotedar, 1971 (Figs. 12–14). 3a. Anterior extent of vitellarium does not exceed bifurcal level; ovary distant from ventral sucker and closer to anterior testis.................................................................................................... 4. 3b. Anterior extent of vitellarium pre-bifurcal and can reach to pharyngeal level; ovary contiguous with or very close to ventral sucker and more distant from anterior testis............... Astiotrema impletum (Looss, 1899) Looss, 1900 (Figs. 6–11). 4a. Anterior extent of vitellarium bifurcal; oral sucker distinctly larger than ventral sucker; parasitizes marine turtles........................................... Astiotrema karachiensis Bilqees, Khatoon & Khan, 2002 n. comb. (Figs. 26 & 27). 4b. Anterior extent of vitellarium post-bifurcal; suckers roughly equal in size; parasitizes freshwater turtles and fish...................................................................... Astiotrema odhneri Bhalerao, 1936 (Figs. 17–20). 5a. Anterior extent of vitellarium pre-ovarian but does not reach pre-bifurcal level, posterior extent terminates anterior to cecal ends.............................................................................................. 6. 5b. Anterior extent of vitellarium pre-bifurcal, posterior extent terminates at cecal ends or slightly further posteriorly........................................................................ Astiotrema fotedari Dhar, 1977 (Figs. 23–25). 6a. Genital pore immediately anterior to ventral sucker; ventral sucker relatively close to intestinal bifurcation............. 7. 6b. Genital pore anterior to ventral sucker by a distinct distance; ventral sucker distant from intestinal bifurcation...................................................................... Astiotrema cyclemysi Siddiqi, 1965 (Figs. 21 & 22). 7a. Esophagus distinct, long; anterior extent of vitellarium does not reach anterior to ventral sucker; ovary smaller than testes.......................................... Astiotrema reniferum (Looss, 1898) Looss, 1900 [type species] (Figs. 1–5). 7b. Esophagus indistinct or very short; anterior extent of vitellarium reaches anterior to ventral sucker and is confluent medially in pre-acetabular region; ovary and testes roughly equal in size........... Astiotrema emydis Ejsmont, 1930 (Figs. 15 & 16)., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2021, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto), pp. 36-72 in Zootaxa 4991 (1) on pages 59-60, DOI: 10.11646/zootaxa.4991.1.2, http://zenodo.org/record/5027482, {"references":["Looss, A. (1900) Nachtragliche Bemerkungen zu den Namen der von mir vorgeschlagenen Distomidengattungen. Zoologischer Anzeiger, 23, 601 - 608.","Mehra, H. R. & Negi, P. S. (1926) On a new trematode Tremiorchis ranarum nov. gen, nov. spec., from the common Indian frog Rana tigrina. Parasitology, 18, 168 - 181. https: // doi. org / 10.1017 / s 0031182000005126","Fotedar, D. N. (1971) On the synonymy of the trematode genera Astiotrema Looss, 1900 and Tremiorchis Mehra and Negi, 1925, and notes on the existing species of the genus. Journal of Parasitology, 57, 39 - 40.","Looss, A. (1899) Weitere Beitrage zur Kenntnis der Trematodenfauna Aegyptens, zugleich Versuch einer naturlichen Gliederung des Genus Distomum Retzius. Zoologische Jahrbucher, 12, 521 - 784. https: // doi. org / 10.5962 / bhl. part. 2037","Bilqees, F. M., Khatoon, N. & Khan, A. (2002) Astioglossimetra karachiensis n. gen., n. sp. (Trematoda: Plagiorchiidae: Astiotrematinae) from the marine turtle Chelonia mydas of Karachi Coast. Turkish Journal of Zoology, 26 (3), 279 - 282.","Bhalerao, G. D. (1936) Studies on the helminths of India. Trematoda II. Journal of Helminthology, 14, 181 - 206. https: // doi. org / 10.1017 / s 0022149 x 00004089","Dhar, R. L. (1977) Astiotrema fotedari n. sp. (Trematoda: Plagiorchidae Luhe, 1901) from the intestine of Labeo dero (Hemilton). Journal of Science, University of Kashmir, 3, 99 - 104.","Siddiqi, A. H. (1965) A new species of the genus Astiotrema Looss, 1900 with a key to its species. Journal of Helminthology, 39, 113 - 116. https: // doi. org / 10.1017 / s 0022149 x 00020101","Looss, A. (1898) Quelques observations a propos de la note: Forme nouve etc. de entozoi d'Egitto de Mr le docteur Sonsino dans Ce Journal. 1896. Centralblatt fur Bakteriologie, Parasitenkunde und Infektionskrankheiten, 23, 453 - 461.","Ejsmont, L. (1930) Astiotrema emydis n. sp., ein trematode aus Emys orbicularis L. Bulletin International de l'Academie Polonaise des Sciences des Lettres, Classe des Sciences Mathematiques et Naturelles. II, Zoologie. Polska Akademia Umiejetnosci, Krakow. Wydzial Matematyczno-Przyrodniczy. Bulletin International, Krakow, Series B- 2, 2, 405 - 417."]}

Astiotrema ranarum (Mehra & Negi, 1926) Fotedar, 1971 (Figs. 12–14) (Syns.: Centrovitus pentadelphi Bhalerao, 1926; Tremiorchis ranarum Mehra & Negi, 1926; Tremiorchis mehrai Rai, 1962; Tremiorchis vitelloconfluentum Rai, 1962; Tremiorchis attenuatus Karyakarte, 1973; Tremiorchis tigrinarum Sinha, Sahay & Prasad, 1974; Tremiorchis mathuraensis Swaroop & Jain, 1976; Tremiorchis tigrinarum andersoni Lal, 1977 n. syn.; Tremiorchis spiniphlyctis Kalyankar & Palladwar, 1978; Astiotrema siddiqii Lal & Prasad, 1980 n. syn.; Tremiorchis jamshedpurensis Hasnain, 1989 n. syn.; Tremiorchis fatimae Bilqees & Khan, 2003 n. syn.) Records (see Table 1): 1. Bhalerao (1926); 2. Mehra & Negi (1926, 1936); 3. Verma (1930); 4. Singh (1954); 5. Bhardwaj (1962); 6. Rai (1962); 7. Agrawal (1968); 8. Ali & Karykarte (1970); 9. Dwivedi & Chauhan (1970); 10. Mukherjee & Ghosh (1970); 11. Fotedar (1971); 12. Sinha & Sahay (1971); 13. Pandey (1973); 14. Rao (1974); 15. Sinha et al. (1974); 16. Bhutta & Khan (1975); 17. Swaroop & Jain (1976); 18. Khan & Haksar (1977); 19. Lal (1977); 20. Singh (1977); 21. Kalyankar & Palladwar (1978); 22. Singh & Sinha (1979); 23. Karyakarte & Baheti (1980); 24. Lal & Prasad (1980); 25. Hafeezullah & Dutta (1981); 26. Hasnain (1989); 27. Rajendran & Janardanan (1993); 28. Bilqees & Khan (2003); 29. Pandey & Agrawal (2013); 30. Pandey et al. (2013); 31. Hemalatha et al. (2015). Remarks: Bhardwaj (1962) examined T. ranarum and reported intra-specific variations and abnormalities including (i) differences in size of body and organs, (ii) minor differences in sucker ratio, (iii) presence or absence of a prepharynx, (iv) slight changes in extent of intestinal ceca, cirrus-pouch and vitellarium, (v) confluent nature of the vitelline follicles, (vi) differences in position, size and shape of gonads as well as degree of lobulation of testes, (vii) slight variations in size and shape of the egg, (viii) differences in the posterior extent of the cirrus-pouch relative to the ventral sucker (either more dorsal or lateral to it), and (viii) degree and posterior extent of spines on the body. In light of the work of Bhardwaj (1962), Mukherjee & Ghosh (1970) considered both T. mehrai and T. vitelloconfluentum as synonyms of T. ranarum and transferred T. varanum into Astiotrema as A. varanum (see above). Pandey & Agrawal (1981) presented a detailed discussion and review of Tremiorchis. This study focused on the slight morphological spectrum observed in some features which previously were considered differential characters between several species of Tremiorchis. Pandey & Agrawal (1981) attributed the observed variations noted by Bhardwaj (1962) to the degree of maturity of the worm, poor sample size and errors in preparation of parasites, particularly fixation. Based on the invalidity of characterizing species based on such slight variations, Pandey & Agrawal (1981) accepted the synonymy of T. mehrai and T. vitelloconfluentum with T. ranarum and also synonymized T. tigrinarum, T. mathuraensis and T. spiniphlyctis with T. ranarum, the only representative of Tremiorchis. In another revision of Tremiorchis, Hafeezullah & Dutta (1981) referred to the synonymy of T. attenuatus, T. tigrinarum and T. mathuraensis with T. ranarum as an indicator of the monotypy of Tremiorchis. To explain the variability among these four species, Hafeezullah & Dutta (1981) attributed these variations to human error during sample preparation as represented by the different states of contraction or relaxation among the specimens, evidence of excessive pressure applied and the incorrect orientation of the fluke during the mounting process. Fotedar (1971) synonymized Tremiorchis with Astiotrema and recognized T. ranarum as A. ranarum, and although this synonymy was rejected by Pojmańska (2008), we accept it based on the results of Besprozvannykh et al. (2015) and similarities with life-cycle patterns elucidated by Rajendran & Janardanan (1993). Astiotrema ranarum is easily characterized as follows: (i) oral sucker slightly smaller than ventral sucker, (ii) vitelline fields short and extend from level of ventral sucker to posterior limit of pretesticular level, (iii) ceca short and terminate at level of anterior testis, (iv) ovary either contiguous with ventral sucker or posterior to it by a small distance and (v) esophagus long and straight. Lal (1977) described a new subspecies, T. tigrinarum andersoni, based on what was interpreted as intra-specific morphological variations observed in specimens of T. tigrinarum (= T. ranarum) from the intestine of the smooth-sided or spotted toad, Rhaebo guttatus (Schneider) (Syn. Bufo anderssoni Melin) (Anura: Bufonidae). Hasnain (1989) added T. jamshedpurensis for specimens gathered from the intestine of the common or Indian skittering frog, E. cyanophlyctis (Anura: Dicroglossidae), in Jamshedpur, ‎ Jharkhand, India. Bilqees & Khan (2003) described T. fatimae for specimens collected from the small intestine of the same host, E. cyanophlyctis, in Karachi, Sindh, Pakistan, and distinguished it from T. ranarum by its longer body, suckers of slightly smaller size and its slightly larger eggs. In light of the wide range of intra-specific variability observed in T. ranarum (Bhardwaj 1962; Hafeezullah & Dutta 1981; Pandey & Agrawal 1981) and the common geographical distribution as well as records from common hosts, we interpret T. tigrinarum andersoni , T. jamshedpurensis and T. fatimae as synonyms of T. ranarum . Lal & Prasad (1980) erected A. siddiqii for two specimens collected from the intestine of E. cyanophlyctis in Patna, Bihar, India. We found this species morphologically to be identical to A. ranarum except in having an indistinct esophagus and the anterior extent of the vitellarium is to the level of the intestinal bifurcation. We also note the poor sample size and the contracted status of their specimens (see Lal & Prasad 1980, fig. 1). Specifically, it seems that the anterior portion of the body is deformed and more contracted, producing a shortened esophagus, the ventral sucker and intestinal bifurcation overlap, and both the ventral sucker and vitelline fields are positioned more anteriorly. In addition, this species shares the same host group (dicroglossid frogs) and locality (India) with A. ranarum. Thus, we consider A. siddiqii another synonym of A. ranarum . Astiotrema ranarum is morphologically similar to A. impletum, but the latter differs by having (i) an oral sucker much larger than the ventral sucker rather than vice versa, (ii) the anterior extent of the vitellarium reaching the level of the pharynx and not the level of the ventral sucker, (iii) a large seminal vesicle occupying almost the entire cirrus-pouch and not a small one occupying about 1/3 of it, (iv) ceca ending immediately posterior to or near the level of the posterior testis vs in the area anterior to the anterior testis, (v) a sigmoid esophagus vs a straight one, and (vi) A. impletum is known from fish (globe fish), reptiles (monitor lizards) and anurans (Asian common toad), whereas A. ranarum is restricted to amphibians only., Published as part of Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2021, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto), pp. 36-72 in Zootaxa 4991 (1) on pages 48-50, DOI: 10.11646/zootaxa.4991.1.2, http://zenodo.org/record/5027482, {"references":["Mehra, H. R. & Negi, P. S. (1926) On a new trematode Tremiorchis ranarum nov. gen, nov. spec., from the common Indian frog Rana tigrina. Parasitology, 18, 168 - 181. https: // doi. org / 10.1017 / s 0031182000005126","Fotedar, D. N. (1971) On the synonymy of the trematode genera Astiotrema Looss, 1900 and Tremiorchis Mehra and Negi, 1925, and notes on the existing species of the genus. Journal of Parasitology, 57, 39 - 40.","Bhalerao, G. D. (1926) On the trematodes of the digestive tract of a common Indian frog, Rana tigrina, with a description of Centrovitus pentadelphi n. g., n. sp. Parasitology, 18, 154 - 159. https: // doi. org / 10.1017 / s 0031182000005102","Rai, S. L. (1962) On two new species of the genus Tremiorchis Mehra and Negi, 1926. (Trematoda: Plagiorchiidae). Proceedings of the National Academy of Sciences, India, 32, 379 - 384.","Karyakarte, P. P. (1973) Tremiorchis attenulas sp. n. (Trematoda: Plagiorchiidae) from the frog Rana cyanophlyctis in India. Marathwada University Journal of Science, 12, 229 - 232.","Sinha, A., Sahay, U. & Prasad, D. (1974) Studies on the digenetic trematodes of Bihar. Indian Journal of Animal Research, 8, 39 - 44.","Swaroop, M. & Jain, S. P. (1976) Tremiorchis mathuraensis n. sp. (Trematoda; Plagiorchiidae) from the common Indian frog Rana tigrina (Daud). Agra University Journal of Research (Science), 25, 99 - 102.","Lal, A. K. (1977) On the occurrence of Tremiorchis tigrinarum var. andersoni var. n. (Trematoda: Plagiorchiidae) from Bufo andersoni. Indian Journal of Zootomy, 18, 77 - 79.","Lal, A. K. & Prasad, D. (1980) On Astiotrema siddiqii n. sp. (Plagiorchidae, Astiotrematinae, Trematoda) from Rana cyanophlyctis. Indian Journal of Helminthology, 32, 93 - 95.","Hasnain, M. (1989) On a new species of Tremiorchis from the intestine of Rana cyanophlyctis. Indian Journal of Helminthology, 41, 78 - 82.","Bilqees, F. M. & Khan, A. (2003) On two new digenetic trematodes from amphibians of Sindh, Pakistan. Pakistan Journal of Zoology, 35, 211 - 213.","Singh, K. S. (1954) Some trematodes collected in India. Transactions of the American Microscopical Society, 73, 202 - 210. https: // doi. org / 10.2307 / 3223758","Bhardwaj, O. N. (1962) Studies of intraspecific variations in Tremiorchis ranarum Mehra et Negi, 1926 (Plagiorchidae Luhe, emend Ward, 1917: Trematoda) and discussion on causes and effects of intraspecific variations. Proceedings of the National Academy of Sciences, 32, 445 - 450.","Agrawal, V. (1968) On some trematode parasites of Amphibia from Lucknow. Revista de Biologia Tropical, 15, 1 - 11.","Dwivedi, M. P. & Chauhan, B. S. (1970) On some digenetic trematodes. Part II. Zoological Society of India, 21, 81 - 96.","Mukherjee, R. P. & Ghosh, R. K. (1970) Studies on some amphibian trematodes from Uttar Pradesh and West Bengal. Indian Journal of Helminthology, 22, 61 - 78.","Sinha, A. & Sahay, U. (1971) On the occurrence of Tremiorchis ranarum Mehra et Negi 1926 from Rana cyanophlyctis at Putna. Indian Journal of Helminthology, 23, 56 - 59.","Pandey, K. C. (1973) Studies on some known and unknown trematode parasites. Indian Journal of Zootomy, 14, 197 - 219.","Rao, L. N. (1974). A note on the characterization of oocytes in three trematodes of Rana tigrina. Current Science, 43, 158 - 159.","Bhutta, M. S. & Khan, D. (1975) Digenetic trematodes of vertebrates from Pakistan. Bulletin of the Department of Zoology, University of the Panjab, New Series, 8, 1 - 175.","Khan, A. & Haksar, C. (1977) Studies on distribution of protein in a digenetic trematode Tremiorchis ranarum (Mehra et Negi 1926). American Zoologist, 17, 925 - 925.","Singh, M. S. (1977) Studies on the amphibian trematodes from Tamil Nadu and Kerala. Records of the Zoological Survey of India, 72, 291 - 294.","Singh, S. P. & Sinha, D. P. (1979) Observations on egg-shell formation in Ganeo tigrinum, Mehraorchis ranarum, Tremiorchis ranarum and Halipegus mehransis [India]. Indian Journal of Animal Research (India), 13, 27 - 30.","Karyakarte, P. P. & Baheti, S. P. (1980) Studies on free amino acids in Tremiochis ranarum, Mehra and Negi, 1926 (Trematoda: Digenea). Rivista di Parasitologia, 41, 81 - 83.","Hafeezullah, M. & Dutta, I. B. (1981) On the monotypy of the genera Anchitrema Looss, 1899 and Tremiorchis Mehra and Negi, 1926 with a note on Pleurogenes Pleurogenoides-Indopleurogenes-Alloindopleurogenes complex. Bulletin of the Zoological Survey of India, 4, 165 - 171.","Rajendran, K. V. & Janardanan, K. P. (1993) Studies on the life-cycle of Tremiorchis ranarum. Journal of Helminthology, 67, 95 - 101. https: // doi. org / 10.1017 / s 0022149 x 00012955","Pandey, K. C. & Agrawal, N. (2013) Metacercarial fauna of India. Records of Zoological Survey of India, 349, 1 - 310.","Pandey, D., Pandey, J. P. & Shukla, N. (2013) Morphological intraspecific variation of Tremiorchis ranarum from Rana tigrina in District Sidhi (MP) India. International Journal of Scientific and Research Publications, 3, 1 - 3.","Hemalatha, M., Srinivasa, K. C. & Anuprasanna, V. (2015) Occurrence and seasonal dynamics of the digenean, Tremiorchis ranarum Mehra et Negi, 1926 (Digenea: Plagiorchiidae) in the Indian bull frog, Hoplobatrachus tigerinus Daudin, 1803 from Kadapa District, Andhra Pradesh, India. Species, 12, 45 - 51.","Pandey, K. C. & Agrawal, N. (1981) Further remarks on the genus Tremiorchis Mehra and Negi, 1925. Proceedings: Animal Sciences, 90, 567 - 570. https: // doi. org / 10.1007 / BF 03186037","Besprozvannykh, V. V., Atopkin, D. M., Ermolenko, A. V., Kharitonova, A. V. & Khamatova, A. Y. (2015) Life-cycle and genetic characterization of Astiotrema odhneri Bhalerao, 1936 sensu Cho & Seo 1977 from the Primorsky region (Russian far east). Parasitology International, 64, 533 - 539. https: // doi. org / 10.1016 / j. parint. 2015.07.008"]}

Species of Astiotrema Looss, 1900 (sensu lato) infect a wide range of fishes, amphibians and reptilians. They also possess a considerably wide spectrum of morphological features. Several species were recognized for variable, confusing, overlapping and unspecialized morphological characters rather than for unique distinguishing features, causing continuing dispute around the validity of several species. Following comprehensive review, a revised restricted concept of Astiotrema is proposed including a morphologically strict definition. Both Tremiorchis Mehra & Negi, 1926 and Astioglossimetra Bilqees, Khatoon & Khan, 2002 are synonymized with Astiotrema (sensu stricto). Several nominal species are synonymized, others are excluded and characters for each recognized species are presented and explained. Only eight species are recognized: Astiotrema cyclemysi Siddiqi, 1965, Astiotrema emydis Ejsmont, 1930, Astiotrema fotedari Dhar, 1977, Astiotrema impletum (Looss, 1899) Looss, 1900, Astiotrema karachiensis (Bilqees, Khatoon & Khan, 2002) n. comb., Astiotrema odhneri Bhalerao, 1936, Astiotrema ranarum (Mehra & Negi, 1926) Fotedar, 1971 and Astiotrema reniferum (Looss, 1898) Looss, 1900. A key to the species of Astiotrema (sensu stricto) is presented, a comprehensive list of all host-locality records is included and host-parasite specificity is elucidated.

Choledocystus simulans Freitas, 1941 Hosts (prevalence; range): L. podicipinus (2/225; 1), L. fuscus (1/50; 1), and E. bicolor (1/40; 3). Site of infection: small intestine and stomach. Stage: juvenile. Type host and type locality: L. latras, Montevideo, Uruguay. Comments: Choledocystus simulans was described as Glypthelmins simulans by Freitas (1941), and then Razo- Mendivil et al. (2006) placed it in Choledocystus by the features of this genus such as tegument with triangular spines extending from anterior to posterior region, suckers with similar size, globular cirrus sac, dextral ovary and Y-shaped excretory vesicle opened for a subterminal pore (Razo-Mendivil et al. 2006). Other features such as lateral pore in relation to acetabulum, entire seminal vesicle, and absence of seminal receptacle can distinguish Choledocystus from Glypthelmins and Rauschiella (Razo-Mendivil et al. 2006; Razo-Mendivil & Pérez-Ponce de Léon 2008). Furthermore, the specimens of our study presented the main features of C. simulans which are globular seminal vesicle, testes close with each other and with ovary, well developed vitelline follicles from the level of intestinal bifurcation not reaching the end of the body, and caeca ending in posterior extremity of body (Freitas 1941; Travassos et al. 1969). Leptodactylus podicipinus, L. fuscus, and E. bicolor are new hosts for C. simulans., Published as part of Aguiar, Aline, Morais, Drausio Honorio, Firmino Silva, Lidiane A., Anjos, Luciano Alves Dos, Foster, Ottilie Carolina & Silva, Reinaldo José Da, 2021, Biodiversity of anuran endoparasites from a transitional area between the Atlantic Forest and Cerrado biomes in Brazil: new records and remarks, pp. 1-41 in Zootaxa 4948 (1) on page 21, DOI: 10.11646/zootaxa.4948.1.1, http://zenodo.org/record/4616068, {"references":["Razo-Mendivil, U. J., Leon-Regagnon, V. & Perez-Ponce de Leon, G. (2006) Monophyly and systematic position of Glypthelmins (Digenea), based on partial lsrDNA sequences and morphological evidence. Organisms, Diversity & Evolution, 6, 308 - 320. https: // doi. org / 10.1016 / j. ode. 2005.12.005","Razo-Mendivil, U. J. & Perez-Ponce de Leon, G. (2008) Taxonomic revision of the genus Glypthelmins Stafford, 1905 (Platyhelminthes: Digenea: Plagiorchiida), parasites of anurans in the Americas. Zootaxa, 1882 (1), 1 - 45. https: // doi. org / 10.11646 / zootaxa. 1882.1.1","Travassos, L., Freitas, J. F. T. & Kohn, A. (1969) Trematodeos do Brasil. Memorias do Instituto Oswaldo Cruz, 67, 1 - 886."]}

Choledocystus cf. elegans (Travassos, 1926) Ruiz, 1949 Hosts (prevalence; range): P. platensis (26/35; 1–6). Site of infection: small intestine and lungs. Stage: adult. Type host and type locality: L. latrans (= L. ocellatus), S„o Paulo, Brazil. Comments: Choledocystus elegans was described as Glypthelmins elegans by Travassos (1926). After, Pereira & Cuocolo (1941) established the genus Choledocystus, and Ruiz (1949) considered G. elegans as C. elegans due to a set of features such as tegument with spines from anterior to posterior end, wide pharynx, large caeca reaching posterior region, globular cirrus sac anterior to acetabulum, dextral ovary, and Y-shaped excretory vesicle with branches reaching the testes; the most of these features were observed in our specimens which lead us to determine C. cf. elegans. However, several taxonomic debates have concerned these plagiorchioids (Choledocystus, Glypthelmins, and Rauschiella); according to Razo-Mendivil et al. (2006) some characters such as ovary position, features of spines in tegument, the type of excretory vesicle, and the extension of uterine loops can help to distinguish these genera. Considering these complex taxonomic relations among plagiorchiids, we encourage species confirmation with molecular and SEM analyses in some cases. This is the first record of C. cf. elegans in P. platensis; other records for this parasite were in L. latrans, Leptodactylus labyrinthicus (Spix) and R. marina from Argentina and Brazil (see Campi„o et al. 2014) and Leptodactylus paraensis Heyer from Pará State, Brazil (Gomes et al. 2017)., Published as part of Aguiar, Aline, Morais, Drausio Honorio, Firmino Silva, Lidiane A., Anjos, Luciano Alves Dos, Foster, Ottilie Carolina & Silva, Reinaldo José Da, 2021, Biodiversity of anuran endoparasites from a transitional area between the Atlantic Forest and Cerrado biomes in Brazil: new records and remarks, pp. 1-41 in Zootaxa 4948 (1) on page 21, DOI: 10.11646/zootaxa.4948.1.1, http://zenodo.org/record/4616068, {"references":["Travassos, L. (1926) Trematodeos novos. (V). Boletim Biologico, 1, 16 - 19.","Ruiz, J. M. (1949) Consideracies sobre o genero Choledocystus Pereira & Cuocolo, 1941 (Trematoda, Plagiorchiidae). Revista Brasileira de Biologia, 9, 167 - 174.","Pereira, C. & Cuocolo, R. (1941) Processo papilomatoso das vias biliares de \" Leptodactylus ocellatus (L.), determinado por Choledocystus eucharis, n. g., n. sp. (Trematoda: Plagiorchiidae). Arquivos do Instituto Biologico, 12, 311 - 324.","Razo-Mendivil, U. J., Leon-Regagnon, V. & Perez-Ponce de Leon, G. (2006) Monophyly and systematic position of Glypthelmins (Digenea), based on partial lsrDNA sequences and morphological evidence. Organisms, Diversity & Evolution, 6, 308 - 320. https: // doi. org / 10.1016 / j. ode. 2005.12.005","Gomes, T. F. F., Melo, F. T. V., Giese, E. G., Furtado, A. P. & Santos, J. N. (2017) Choledocystus elegans (Digenea: Plagiorchiidae) of Leptodactylus paraensis (Amphibia: Leptodactylidae) from the Brazilian Amazon. Brazilian Journal of Veterinary Parasitology, 26 (4), 511 - 515. https: // doi. org / 10.1590 / s 1984 - 29612017049"]}

Choledocystus vitellinophilum (Dobbin Jr., 1958) Hosts (prevalence; range): B. raniceps (1/79; 2). Site of infection: small intestine. Stage: adult. Type host and type locality: B. raniceps (= Hyla raniceps), Pernambuco State, Brazil. Comments: this species was originally described as Glypthelmins vitellinophilum, however, according to Razo- Mendivil et al. (2006) it presents the diagnosis features of Choledocystus. Therefore, we analysed the following characters of C. vitellinophilum in our specimens: the distribution of vitelline follicles which extend from the pharynx level to the end of caeca, position of ovary in relation to acetabulum, relative position of testes, and transversal uterine loops which can overlap the caeca. Until now, this species was known only for the type locality and Argentina (in Lysapsus limellum Cope) (Hamann 2006)., Published as part of Aguiar, Aline, Morais, Drausio Honorio, Firmino Silva, Lidiane A., Anjos, Luciano Alves Dos, Foster, Ottilie Carolina & Silva, Reinaldo José Da, 2021, Biodiversity of anuran endoparasites from a transitional area between the Atlantic Forest and Cerrado biomes in Brazil: new records and remarks, pp. 1-41 in Zootaxa 4948 (1) on page 22, DOI: 10.11646/zootaxa.4948.1.1, http://zenodo.org/record/4616068

Made available in DSpace on 2021-06-25T10:49:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Jiangsu Overseas Research and Training Program for University Prominent Young and Middle-aged Teachers and Presidents Two digenean species, Infidum infidum Faria, 1910 (Dicrocoeliidae) and Travtrema stenocotyle Cohn, 1902 (Plagiorchiidae), were collected in the large pit viper Bothrops moojeni Hoge, 1966 from Reserva Particular do Patrimônio Natural Cisalpina, municipality of Brasilândia, Mato Grosso do Sul State, Brazil. In this study, we provide the first molecular characterisation using the 28S rDNA and phylogenetic position data of these two common digeneans from B. moojeni. The molecular framework revealed topologies with strongly supported clades using maximum likelihood and Bayesian inference methods, positioned I. infidum among Plagiorchiidae and not among Dicrocoeliidae as expected and T. stenocotyle (Plagiorchiidae) surprisingly grouped as a sister group to Allassogonoporidae, Microphallidae, Pleurogenidae, and Prosthogonimidae, not related to plagiorchids. Our molecular phylogenetic data showed that these species may not correspond to their assigned families and encourage future studies on the systematic of these understudied groups. Institute of Biosciences Section of Parasitology São Paulo State University (UNESP), Rua Professor Doutor Antônio Celso Wagner Zanin, 250, Botucatu Department of Biological Sciences Federal University of São Paulo (UNIFESP), Rua Professor Arthur Riedel, 275, Jardim Eldorado, Diadema Instituto de Ciências Agrárias Universidade Federal de Uberlândia (UFU), LMG-746, Km 1 Institute of Biosciences Section of Parasitology São Paulo State University (UNESP), Rua Professor Doutor Antônio Celso Wagner Zanin, 250, Botucatu FAPESP: 2017/16546-3 FAPESP: 2018/00754-9 FAPESP: 2018/09623-4 CNPq: 309125/2017-0 CNPq: 313241/2018-0 CAPES: AUX-PE-PNPD #3005/2010 Jiangsu Overseas Research and Training Program for University Prominent Young and Middle-aged Teachers and Presidents: PROPE-UNESP #02/2016

Haplometra cylindracea (Zeder, 1800) Intermediate host: Lymnaea stagnalis (Gastropoda: Lymnaeidae). Cercarian group: xiphidiocercaria. Habitat: freshwater. Definitive host group: amphibians. Localities: central and northeastern regions. References: Nasimov (1967), Shakarbaev et al. (2013, 2014 b)., Published as part of Shakarbaev, U. A., Akramova, F. D. & Azimov, D. A., 2020, The Taxonomic Survey Of The Cercarial Fauna (Platyhelminthes, Trematoda) In The Mollusks Of Uzbekistan, pp. 505-522 in Zoodiversity 54 (6) on page 516, DOI: 10.15407/zoo2020.06.505, http://zenodo.org/record/6377780, {"references":["Nasimov, Kh. 1967. The trematode larvae of the freshwater molluscs of Samarkand and Bukhara Provinces, Uzbek SSR. PhD Thesis in Biology, 1 - 27 [In Russian].","Shakarbaev, U. A., Safarova, F. E., Akramova, F. D., Shkarboyev, E. B., Golovanov, V. I., Azimov, D. A. 2013. The trematode cercariae developing in molluscs of the family Lymnaeidae Rafinesque, 1845 from the water bodies of the Syrdarya River. Russian Parasitological Magazine. Moscow, 4, 30 - 33 [In Russian].","Shakarbaev, U. A., Akramova, F. D. 2014 b. The species diversity of the trematode cercariae of freshwater molluscs in the water bodies of the northeast of Uzbekistan. Uzbek Biological Journal, 4, 109 - 112 [In Russian]."]}

Shakarbaev, U. A., Akramova, F. D., Azimov, D. A. (2020): The Taxonomic Survey Of The Cercarial Fauna (Platyhelminthes, Trematoda) In The Mollusks Of Uzbekistan. Zoodiversity 54 (6): 505-522, DOI: 10.15407/zoo2020.06.505, URL: https://www.mendeley.com/catalogue/211a61f7-fdfb-3bae-a25a-e93f947ffa77/

Tremiorchis is a monotypic genus of digenetic trematode (Plagiorchiidae: Plagiorchiinae), infecting the frogs Rana tigrina (Hoplobatrachus tigerinus) and R. cyanophlyctis (Euphlyctis cyanophlyctis). Metacercaria use to infect Rana tigrina (Hoplobatrachus tigerinus) and R. cyanophlyctis (Euphlyctis cyanophlyctis) as intermediate hosts, while the cercaria stage found from apple snail, Pila virens. Adults of T. ranarum harbor mature frogs of H. tigerinus and E. cyanophlyctis. Besides the frequent infection of Tremiorchis, no DNA sequence data are currently available for this monotypic genus. The present communication, deals with the sequence data for nuclear ribosomal genes, 18S, small internal transcribed spacers (ITS1–5.8S-ITS2) and 28S to molecularly characterize T. ranarum. Besides this, phylogenetic relationship among the members of the Plagiorchiida is also discussed in detail. An attempt has also been made to provide detailed molecular affinities of T. ranarum with other trematode genera.

During a survey of helminth parasites of the brown ground snake, Atractus major Boulenger, 1894 (Serpentes: Dipsadidae) from Moyobamba, region of San Martin (northeastern Peru), a new species of Glossidiella Travassos, 1927 (Plagiorchiida: Plagiorchiidae) was found and is described herein based on morphological and ultrastructural data. The digeneans found in the lung were measured and drawings were made with a drawing tube. The ultrastructure was studied using scanning electron microscope. Glossidiella peruensissp. nov. is easily distinguished from the type- and only species of the genus, Glossidiella ornata Travassos, 1927, by having an oblong cirrus sac (claviform in G. ornata), distinctly ovate testes (rounded testes in G. ornata) and button-like papillae on the dorsal edge of the oral sucker region (absent in G. ornata). In addition, G. peruensissp. nov. differs from G. ornata by possessing a longer distance between testes and substantially wider oral and ventral suckers. This is the first time that a species of digenean is described and reported parasitizing snakes in Peru.

Summary This paper describes the occurrence of Enodiotrema megachondrus (Looss, 1899) Looss, 1901 in a juvenile green sea turtle (Chelonia mydas Linnaeus, 1758) found on the coast of Brazil. This parasite has been described in Caretta caretta from Egypt, France, the Mediterranean Sea, the Madeira Archipelago, the Adriatic Sea and the USA, in C. mydas from Egypt and the USA, in Eretmochelys imbricata from Cuba, in Lepidochelys olivacea from Mexico and Costa Rica and in Lepidochelys kempii from USA. This note represents the first report of E. megachondus in a green sea turtle in the South-West Atlantic Ocean.

Haematoloechus caballeroi Skrjabin & Antipin, 1962 (Figs. 4 & 5) Type host: Tlaloc��s leopard frog Rana tlaloci Hillis & Frost recorded as Montezuma leopard frog Rana montezumae (Caballero, 1942b; Skrjabin & Antipin, 1962). Type locality: Xochimilco, Mexico City, Mexico (Caballero, 1942b; Skrjabin & Antipin, 1962). Site of infection: lungs. Neotype: CNHE 10457. Paratypes: CNHE 1428, 1551, 1552, 3376���3379, 3395, 3397, 3399, 3794, 4661, 10458���10460. Other hosts and localities: Montezuma leopard frog R. montezumae, Zempoala, Morelos (CNHE 10464), Patzcuaro leopard frog R. dunni Zweifel, P��tzcuaro, Michoac��n (CNHE 10465); R. dunni, Zacapu, Michoac��n (CNHE 10463). Other records: Mexico: Tlaloc��s leopard frog R. tlaloci, Xochimilco, Mexico City (Caballero &Sokoloff 1934 as H. complexus); Montezuma leopard frog R. montezumae, Ci��naga de Lerma, Mexico State (Le��n- R��gagnon 1992 as H. complexus; Lamothe et al. 1997 as H. coloradensis Cort, 1915; Le��n-R��gagnon et al. 1999 as H. complexus; P��rez-Ponce de Le��n et al. 2000 as H. coloradensis and H. complexus); big-footed leopard frog R. megapoda, Cointzio Springs, Michoac��n (P��rez-Ponce de Le��n et al. 2000 as H. complexus); Transverse Volcanic leopard frog R. neovolcanica, Cointzio Springs, Michoac��n (P��rez-Ponce de Le��n et al. 2000 as H. complexus); Patzcuaro leopard frog R. dunni, P��tzcuaro, Michoac��n (Garc��a-Altamirano et al. 1993; Pulido���Flores 1994; P��rez-Ponce de Le��n et al. 2000 as H. coloradensis); Lerma Lake salamander Ambystoma lermaense, Ci��naga de Lerma, Mexico State (P��rez-Ponce de Le��n et al. 2000 as H. complexus; Mata-L��pez et al. 2002 as H. complexus). Redescription: Based on 33 mature specimens. Body elongate, with slender anterior region; 2.8���6.6 (5.0) mm long, 0.82���1.88 (1.27) mm of maximum width at testicular region. Tegument covered with thin spines that are larger and more abundant in anterior region; spines easily lost during fixation and staining procedures; 8���16 (13) long. Oral sucker subterminal, round, 243���487 (355) long, 260���511 (387) wide. Pharynx oval, 146���398 (255) long, 130���300 (206) wide; oral sucker/pharynx ratio 1: 0.41���0.86 (0.66). Pharynx and anterior region of esophagus surrounded by gland cells. Esophagus 24���162 (65) long, sometimes obscured by uterus. Ceca bifurcated at 414��� 844 (643) from anterior extremity. Ceca terminate blindly near posterior extremity. Ventral sucker round, 219���438 (313) long, 203���430 (311) wide, at 0.98���2.7 (1.9) mm (30%���47% (37.6%) of BL) from anterior extremity. Oral sucker: ventral sucker length ratio 1: 0.53���1.0 (0.81). Testes 2, oval, slightly lobed in some specimens, oblique, inmmediately posterior to ovary. Anterior testis opposite to ovary, 219���795 (477) long, 170���682 (360) wide. Posterior testis 203���852 (557) long, 203���771 (396) wide. Cirrus sac reach anterior border of ventral sucker, mostly obscured by ascending uterus; internal seminal vesicle, elongate, slightly coiled. Ejaculatory duct strongly muscular, 190���200 (195) long, surrounded by prostatic gland cells. Ovary oval, 243���665 (414) long, 203���763 (313) wide; at 1.1���2.9 (2.1) mm (33%���51% (42%) of BL) from anterior extremity. Seminal receptacle adjacent partially overlapped with ovary; 203���730 (412) long, 138���568 (300) wide. Mehlis gland dorsal to seminal receptacle. Laurer���s canal not observed. Vitellaria in clusters overlapped with each other, distributed laterally, dorsally invade space between ceca in their anterior limit and in post-testicular region. Anterior limit of distribution 390���1607 (1055) (6.5%���28% (21%) of BL) from anterior end. Follicles extend to halfway between posterior testis and posterior end; in some specimens they extend to level of posterior testis on ovarian side of body, and more posteriorly on side opposite to ovary. Descending part of uterus form transverse and diagonal loops on ovarian side of body, partially overlapped with testis, filling intra- and extracecal space towards posterior end of body. Ascending uterus form one or two short diagonal loops oriented anteriorly on each side of body, and continues with transverse or diagonal loops that occasionally invade both sides of body, not totally overlapped with testes or ovary, and fill with transverse loops entire preovarian region. Genital pore median, ventral to pharynx. Eggs dark brown, 31���40 (36) long, 17���23 (20) wide. Excretory vesicle not observed. Excretory pore terminal. Remarks: In their revision of the family Plagiorchiidae L��he, 1901, Skrjabin & Antipin (1962) described Haematoloechus caballeroi based on a specimen that Caballero (1942b) collected from Tlaloc��s leopard frog R. tlaloci in Xochimilco, Mexico, and was originally identified as H. complexus. This description was based on a single specimen, and was not recognized by any later author; all subsequent records of that morphotype from Mexico were assigned to H. complexus or H. coloradensis. Recent molecular and morphological evidence has shown that H. complexus sensu stricto does not occur in Mexico, but that there is a complex of species closely related to H. complexus, most undescribed (Le��n-R��gagnon & Brooks 2003; Bolek & Janovy 2007a; Le��n- R��gagnon 2010; Le��n-R��gagnon & Romero���May��n 2017). The present species is one of those (GenBank AF532138, Le��n-R��gagnon & Brooks 2003). Haematoloechus caballeroi differs from most other species in the genus, but resembles the following 19 species by lacking longitudinal uterine loops that reach the posterior testis: H. arequipensis Ib����ez & C��rdoba, 1979, H. aubriae Bourgat, Roure & Kulo, 1996, H. coloradensis, H. complexus, H. confusus Ingles, 1932, H. danbrooksi, H. dollfusinum (Odening, 1958), H. elongatus Caballero & Sokoloff, 1934, H. fuelleborni (Travassos & Darriba, 1930), H. humboldtensis, H. illimis, H. kernensis Ingles, 1932, H. longicollum, H. medioplexus, H. meridionalis, H. oxyorchis Ingles, 1932, H. parcivitellarius Caballero, 1942, H. pukinensis Ib����ez & C��rdoba, 1979, and H. pulcher. It differs from H. aubriae, H. danbrooksi, H. medioplexus, and H. meridionalis in the large size of the ventral sucker compared to the oral sucker, which is less than one third in those four species vs more than half in H. caballeroi (Table 2) (Stafford 1902; Bourgat et al. 1996; Le��n-R��gagnon et al. 2001; Le��n- R��gagnon & Paredes-Calder��n 2002). Haematoloechus coloradensis, H. confusus, and H. oxyorchis differ from H. caballeroi in the arrangement of the uterine loops, which are strictly intercecal in those species (Cort 1915; Ingles 1932; Bolek & Janovy 2007a), while they invade the extracecal region in H. caballeroi. Haematoloechus caballeroi differs from H. arequipensis in having oval rather than lobed testes (Iba��ez & C��rdoba 1979). It differs from H. illimis and H. dollfusinum in the shape of the ovary, which is lobed in those species (Caballero 1942a) and oval in H. caballeroi. The presence of diagonal uterine loops directed anteriorly at the posterior end of the body differentiates H. caballeroi from H. humboldtensis, H. longicollum, H. parcivitellarius, and H. pulcher, in which the diagonal uterine loops are either absent or directed posteriorly (Caballero 1942b; Bravo���Hollis 1943; Zamparo et al. 2011; Le��n-R��gagnon & Romero���May��n 2017). Haematoloechus caballeroi most closely resembles H. complexus, H. elongatus, H. fuelleborni, H. kernensis and H. pukinensis. It differs from H. fuelleborni, H. complexus and H. elongatus in having a larger pharynx and ventral sucker compared to the oral sucker (1:0.45, 1:0.56, 1:51 & 1:0.5, 1:0.71, 1:0.70 respectively vs 1:0.66 & 1: 0.81 in H. caballeroi) (Travassos & Darriba 1930; Caballero & Sokoloff 1934; Bolek & Janovy 2007a). It also differs from H. fuelleborni in the distribution of the vitellaria; while they are limited to two groups, one anterior to the ventral sucker and other posterior to the testes in the South American species, they are distributed continuously from the anterior region of the ventral sucker to the posterior region of the testes in H. caballeroi. It also differs from H. complexus in the distribution of the vitellaria which are distributed asymmetrically in that species, being more restricted to the ovarian side of the body (Bolek & Janovy 2007a), while in H. caballeroi they reach the posterior region of the testes on both sides of the body. In addition to the differing size of the ventral sucker and pharynx, H. elongatus differs from H. caballeroi in body size, which is much larger in that species (9.5 mm vs 5.1 mm) than in H. caballeroi. Haematoloechus caballeroi differs from H. kernensis in the size of the ventral sucker compared with the oral sucker, which is larger in that species (1:1, vs 1: 0.82 in H. caballeroi). It also differs from H. kernensis in the distribution of the vitellaria, which do not invade the intercecal region in the post-testicular region in that species, and in the arrangement of the uterus, which forms a few diagonal loops in the pre-acetabular and post-testicular region in H. kernensis, while it is filled with transverse and diagonal loops in both areas in H. caballeroi (Ingles 1932). Haematoloechus caballeroi differs from H. pukinensis in the arrangement of the uterine loops; while in H. pukinensis the ascending part of the uterus forms a few transverse loops in the pre-acetabular region (Ib����ez & C��rdoba 1979), in H. caballeroi the ascending uterus entirely fills the pre-acetabular region. The distribution of the vitellaria is also different in H. pukinensis, being more restricted in the ovarian side of the body in that species. ......continued on the next page......continued on the next page H = Hasegawa et al., 2013. L = Le��n-R��gagnon 2010. LB = Le��n-R��gagnon & Brooks 2003. LGA = Le��n-R��gagnon et al. 2005. RLP = Razo-Mend��vil et al. 2004, 2006. T = Tkach et al. 2000. Z = Zikmundova et al. 2014. 1 originally recorded as H. coloradensis. 2 originally recorded as H. cf. complexus. 3 originally recorded as H. varioplexus., Published as part of Le��n-R��gagnon, Virginia & Topan, Janet, 2018, Taxonomic revision of species of Haematoloechus Looss, 1899 (Digenea: Plagiorchioidea), with molecular phylogenetic analysis and the description of three new species from Mexico, pp. 251-302 in Zootaxa 4526 (3) on pages 254-262, DOI: 10.11646/zootaxa.4526.3.1, http://zenodo.org/record/2611615, {"references":["Skrjabin, K. I. & Antipin, D. N. (1962) The superfamily Plagiorchioidea Dollfus, 1930. In: Skrjabin, K. I. (Ed.), Trematodes of animals and man. Vol. 20. Akademy Nauk, CCCR, Moscow, pp. 47 - 163. [in Russian]","Caballero, C. E. (1942 b) Trematodos de las ranas de la Cienaga de Lerma, Estado de Mexico. III. Redescripcion de una forma norteamericana de Haematoloechus y algunas consideraciones sobre Glypthelmins californiensis (Cort, 1919). Anales del Instituto de Biologia de la Universidad Nacional Autonoma de Mexico, 13, 71 - 79.","Caballero, C. E. & Sokoloff, D. (1934) Segunda contribucion al conocimiento de la parasitologia de Rana montezumae con un resumen. Descripcion de una nueva especie y clave del genero Haematoloechus. Anales del Instituto de Biologia de la Universidad Nacional Autonoma de Mexico, 5, 5 - 40.","Leon-Regagnon, V. (1992) Fauna Helmintologica de Algunos Vertebrados Acuaticos de la Cienaga de Lerma, Mexico. Anales del Instituto de Biologia de la Universidad Nacional Autonoma de Mexico, Serie Zoologia, 63, 151 - 153.","Cort, W. W. (1915) North American frog lung flukes. Transactions of American Microscopical Society, 34, 203 - 240. https: // doi. org / 10.2307 / 3221470","Leon-Regagnon, V., Brooks D. R. & Perez-Ponce de Leon, G. (1999) Differentiation of Mexican species of Haematoloechus Loss, 1989 (Digenea: Plagiorchiformes): molecular and morphological evidence. Journal of Parasitology, 85, 935 - 946. https: // doi. org / 10.2307 / 3285832","Perez-Ponce de Leon, G., Leon-Regagnon, V., Garcia-Prieto, L., Razo-Mendivil, U. & Sanchez-Alvarez, A. (2000) Digenean fauna of amphibians from central Mexico: nearctic and neotropical influences. Comparative Parasitology, 67, 92 - 106.","Garcia-Altamirano, I., Perez-Ponce de Leon, G. & Garcia-Prieto, L. (1993) Contribucion al conocimiento de la comunidad de helmintos de dos especies de anfibios endemicos del Lago de Patzcuaro, Michoacan: Rana dunni y Ambystoma dumerilii. Cuadernos Mexicanos de Zoologia, 1, 73 - 80.","Pulido-Flores, G. (1994) Helmintos de Rana dunni especie endemica del lago de Patzcuaro, Michoacan, Mexico. Anales del Instituto de Biologia de la Universidad Nacional Autonoma de Mexico, Serie Zoologia, 65, 205 - 207.","Mata-Lopez, R., Garcia-Prieto, L. & Leon-Regagnon, V. (2002) Infracomunidades de helmintos parasitos de Ambystoma lermaensis (Caudata: Ambystomatidae) en Lerma, Mexico. Revista de Biologia Tropical, 50, 303 - 307.","Leon-Regagnon, V. & Brooks, D. R. (2003) Molecular phylogeny of Haematoloechus Looss, 1899 (Digenea: Plagiorchiidae), with emphasis on North American species. Journal of Parasitology, 89, 1206 - 1211. https: // doi. org / 10.1645 / GE- 95 R","Bolek, M. G. & Janovy, J. J. (2007 a) Small frogs get their worms first: the role of non-odonate arthropods in the recruitment of Haematoloechus coloradensis and Haematoloechus complexus in newly metamorphosed northern leopard frogs, Rana pipiens, and Woodhouse's toads, Bufo woodhousii. Journal of Parasitology, 93, 300 - 312. https: // doi. org / 10.1645 / GE- 1010 R. 1","Leon-Regagnon, V. (2010) Evidence of new species of Haematoloechus (Platyhelminthes: Digenea) using partial cox 1 sequences. Mitochondrial DNA, 21 (Supplement 1), 12 - 17. https: // doi. org / 10.3109 / 19401736.2010.523700","Leon-Regagnon, V. & Romero-Mayen, A. R. (2017) A new species of Haematoloechus Looss, 1899 (Digenea: Plagiorchioidea: Haematoloechidae), a parasite of Rana psilonota Webb and R. zweifeli Hillis, Frost & Webb (Anura: Ranidae) in Mexico. Systematic Parasitology, 94, 567 - 574. https: // doi. org / 10.1007 / s 11230 - 017 - 9724 - 6","Ibanez, H. N. & Cordoba, B. E. (1979) Algunos trematodos de Telmatobius del Sur del Peru. Boletin Peruano de Parasitologia, 1, 54 - 66.","Bourgat, R., Roure, C. & Kulo, D. (1996) Nouvelles donnees sue les trematodes d'amphibiens d'Afrique Occidentale. Description d'Haematoloechus aubriae n. sp. Revue Suisse de Zoologie, 103, 383 - 394.","Ingles, L. G. (1932) Four new species of Haematoloechus (Trematoda) from Rana aurora draytoni from California. University of California Publications in Zoology, 37, 189 - 202.","Odening, K. (1958) Zur systematik von Haematoloechus (Trematoda, Plagiorchiidae). Mitteilungen aus dem Zoologischen Museum in Berlin, 34, 63 - 108. https: // doi. org / 10.1002 / mmnz. 19580340105","Travassos, L. & Darriba, A. R. (1930) Pesquizas helminthologicas realisadas em Hamburgo III. Trematodeos dos generos Pneumonoeces e Ostiolum. Memorias do Instituto Oswaldo Cruz, 23, 237 - 253. https: // doi. org / 10.1590 / S 0074 - 02761930000500002","Stafford, J. (1902) The American representatives of Distomum cygnoides. Zoologische Jahrbuecher Abteilung fuer Systematik Oekologie und Geographie der Tiere, 17, 411 - 424.","Leon-Regagnon, V., Brooks, D. R. & Zelmer, D. A. (2001) Morphological and molecular description of Haematoloechus meridionalis n. sp. (Digenea: Plagiorchioidea: Haematoloechidae) from Rana vaillanti Brocchi of Guanacaste, Costa Rica. Journal of Parasitology, 87, 1423 - 1427. https: // doi. org / 10.1645 / 0022 - 3395 (2001) 087 [1423: MAMDOH] 2.0. CO; 2","Leon-Regagnon, V. & Paredes-Calderon, E. L. (2002) Haematoloechus danbrooksi n. sp. (Digenea: Plagiorchioidea) from Rana vaillanti from Los Tuxtlas, Veracruz, Mexico. Journal of Parasitology, 88, 1215 - 1221. https: // doi. org / 10.1645 / 0022 - 3395 (2002) 088 [1215: HDNSDP] 2.0. CO; 2","Caballero, C. E. (1942 a) Trematodos de las ranas de la Cienaga de Lerma, Estado de Mexico. II. Descripcion de una nueva especie de Haematoloechus. Revista Brasileira de Biologia, 2, 155 - 158.","Bravo-Hollis, M. (1943) Estudio sistematico de los trematodos parasitos de los ajolotes de Mexico (1). Anales del Instituto de Biologia, Universidad Nacional Autonoma de Mexico, 14, 141 - 159.","Zamparo, D., Ferrao, A., Brooks, D. R., Bettaso, J. & Mata-Lopez, R. (2011) New species of Haematoloechus (Digenea: Plagiorchidae) in the lung of the foothill yellow-legged frog Rana boylii (Anura), from Humboldt County, California, USA. Revista Mexicana de Biodiversidad, 82, 445 - 451.","Hasegawa, H., Sato, A., Kai, M. & Uchida, A. (2013) Helminth parasites of bullfrogs, Lithobates catesbeianus (Shaw, 1802), in Kanto District, Japan, with special reference to those introduced from North America. Japanese Journal of Veterinary Parasitology, 12, 1 - 10.","Leon-Regagnon, V., Guillen-Hernandez, S. & Arizmendi-Espinosa, M. A. (2005) Intraspecific variation of Haematoloechus floedae Harwood, 1932 (Digenea: Plagiorchiidae), from Rana spp. in North and Central America. Journal of Parasitology, 91, 915 - 921. https: // doi. org / 10.1645 / GE- 430 R. 1","Razo-Mendivil, U., Leon-Regagnon, V. & Perez-Ponce de Leon, G. (2004) Description of two new species of Glypthelmins Stafford, 1905 (Digenea: Macroderoididae) in Rana spp. from Mexico, based on morphology and mtDNA and rDNA sequences. Systematic Parasitology, 59, 199 - 210. https: // doi. org / 10.1023 / B: SYPA. 0000048099.73779. f 4","Razo-Mendivil, U., Leon-Regagnon, V. & Perez-Ponce de Leon, G. (2006) Monophyly and systematic position of Glypthelmins (Digenea), based on partial lsrDNA sequences and morphological evidence. Organisms, Diversity and Evolution, 6, 308 - 320. https: // doi. org / 10.1016 / j. ode. 2005.12.005","Tkach, V., Pawlowski, J. & Mariaux, J. (2000) Phylogenetic analysis of the Suborder Plagiorchiata (Platyhelminthes, Digenea) based on partial lsrDNA sequences. International Journal for Parasitology, 30, 83 - 93. https: // doi. org / 10.1016 / S 0020 - 7519 (99) 00163 - 0","Zikmundova, J., Georgieva, S., Faltynkova, A., Soldanova, M. & Kostadinova, A. (2014) Species diversity of Plagiorchis Luhe, 1899 (Digenea: Plagiorchiidae) in lymnaeid snails from freshwater ecosystems in central Europe revealed by molecules and morphology. Systematic Parasitology, 88, 37 - 54. https: // doi. org / 10.1007 / s 11230 - 014 - 9481 - 8"]}

Haematoloechus mexicanus n. sp. (Figs. 10 & 11) Type host: Montezuma leopard frog Rana montezumae (=Northern leopard frog R. pipiens Schreber and R. montezumae of Caballero 1941). Type locality: Ciénaga de Lerma, Estado de Mexico, Mexico. Site of infection: Lungs Holotype: CNHE 10489 Paratypes: CNHE 10490, 10491, 10492. Etymology: Species name refers to Estado de Mexico, the province of the type locality. Other hosts and localities: Mexico: Montezuma leopard frog Rana montezumae, Xochimilco, Mexico City (Caballero, 1941, as H. medioplexus); Patzcuaro leopard frog R. dunni, Pátzcuaro, Michoacán (León-Règagnon et al. 1999, as H. coloradensis); Transverse Volcanic leopard frog R. neovolcanica, Cointzio, Michoacán (this study). Description: Based on 17 mature specimens: Body slender, with thinner anterior region; 4.8–8.3 (7.0) mm long, 0.7–1.3 (1.0) mm of maximum width at testicular region. Tegument covered with abundant thin spines, easily lost during fixation; 7.5–12.5 (9.8) long. Oral sucker subterminal, round, 203–350 (284) long, 180–380 (278) wide. Pharynx oval, 140–280 (206) long, 122–220 (183) wide; oral sucker/pharynx ratio 1: 0.74–0.90 (0.83). Anterior border of pharynx and esophagus surrounded by gland cells. Esophagus 41–200 (129) long. Ceca bifurcated at 390–770 (609) from anterior extremity. Ceca terminate blindly near posterior extremity. Ventral sucker small, weakly developed, frequently obscured by uterus, 52–125 (82) long, 57–130 (84) wide, at 1.5–3.0 (2.4) mm (31%– 41% (37%) of BL) from anterior extremity. Sucker length ratio 1:0.28–0.38 (0.33). Testes 2, elliptical, elongate, oblique, posterior to ovary; distance between ovary and anterior testis 350–825 (548). Anterior testis opposite to ovary, 365–1,080 (778) long, 243–600 (451) wide. Posterior testis 422–1200 (863) long, 260–830 (495) wide. Cirrus sac reaches anterior border of ventral sucker, mostly obscured by ascending uterus; internal seminal vesicle, elongate, slightly coiled. Ejaculatory duct weakly muscular, 150–160 (155) long, surrounded by prostatic gland cells. Ovary kidney shaped, lobed, 320–840 (623) long, 162–500 (342) wide; at 1.8–4.3 (2.8) mm (35%–57% (40%) of BL) from anterior extremity. Seminal receptacle posterior, partially overlapped with ovary; 300–1000 (644) long, 250–590 (410) wide. Mehlis gland dorsal to seminal receptacle. Laurer’s canal not observed. Vitellaria in clusters of oval, well defined follicles, distributed laterally, dorsally invade space between ceca in anterior region of ovary and sometimes in post-testicular region. Anterior limit of distribution 982–3200 (1766) (19%–49% (25%) of BL) from anterior end. Follicles extend asymmetrically, to anterior region of posterior testis on ovarian side of body, and halfway between posterior testis and posterior end of body on side opposite to ovary. Uterine loops fill intra- and extracecal space, partially overlap testes and ovary. Descending part of uterus form several diagonal loops that frequently bend anteriorly or posteriorly and form short longitudinal extracecal loops on ovarian side of body. Uterus forms two longitudinal uterine loops on each side of posterior end of body that reach halfway between posterior end and posterior testis; one loop is frequently shorter. Ascending part of uterus forms diagonal loops on side opposite to ovary, frequently bends anteriorly or posteriorly to form longitudinal extracecal loops. Descending and ascending parts of uterus in two lateral fields rarely invade each other. Distal uterus fills intracecal preovarian region with diagonal loops. Genital pore median, ventral to middle region of pharynx. Eggs dark brown, 22–26 (24) long, 14–20 (17) wide. Excretory vesicle not observed. Excretory pore terminal. Remarks: Haematoloechus mexicanus n. sp. resembles those species of the genus possessing short longitudinal or diagonal uterine loops not reaching the posterior testis, namely H. aubriae, H. caballeroi, H. danbrooksi, H. fuelleborni, H. humboldtensis, H. illimis, H. kernensis, H. occidentalis n. sp., H. pukinensis, and H. veracruzanus n. sp. It also resembles those species with a ventral sucker less than half the size of the oral sucker, namely H. combesi Batchvarov & Bourgat, 1974, H. danbrooksi, H. darcheni Combes & Knoepffler, 1967, H. floedae, H. leonensis (Williams & Coker, 1967), H. medioplexus, H. meridionalis, H. nicolasi, H. ocellati Gassmann, 1975 and H. parviplexus (Table 2). This new species differs from H. caballeroi, H. fuelleborni, H. humboldtensis, H. illimis, H. kernensis, H. occidentalis n. sp., H. pukinensis, and H. veracruzanus n. sp. in the size of the ventral sucker compared to the oral sucker, which is smaller in H. mexicanus n. sp. (1: 0.5–1.0 in the other species vs 1: 0.33 in H. mexicanus n. sp.), and it differs from H. aubriae in the presence of ventral sucker, which is absent in that species. It also differs from H. aubriae, H. caballeroi, H. fuelleborni, H. humboldtensis, H. kernensis, H. occidentalis n. sp., H. pukinensis, and H. veracruzanus n. sp. in the shape of ovary and testes, which are oval in those species, while in H. mexicanus n. sp. the ovary is lobed and testes are elliptical or elongate. Haematoloechus mexicanus n. sp. differs from H. combesi, H. darcheni, H. floedae, H. leonensis, H. medioplexus, H. meridionalis, H. nicolasi, H. ocellati and H. parviplexus in the arrangement of the uterine loops. Haematoloechus medioplexus and H. meridionalis lack uterine longitudinal loops (Stafford, 1902; León-Regagnon et al. 2001), in H. combesi, H. floedae and H. leonensis they reach the level of the ovary (Williams & Coker 1967; Batchvarov & Bourgat 1974; León-Règagnon et al. 2005), in H. darcheni and H. ocellati they reach the level of the anterior testis (Combes & Knoepffler 1967; Gassmann 1975), in H. nicolasi and H. parviplexus they reach the level of the posterior testis (Irwin 1929; León-Règagnon 2017), while in H. mexicanus n. sp. they reach halfway between the posterior testis and the posterior end. In this new species there are frequently several short longitudinal uterine loops in the posttesticular region and at the level of testes, which are absent in the other species. Haematoloechus mexicanus n. sp. most closely resembles H. danbrooksi in the size of the ventral sucker and the presence of short diagonal or longitudinal uterine loops in the posterior end of body, but differs from that species in the shape of the ovary, which is oval or slightly bi-lobed in some specimens (León-Règagnon & Paredes-Calderón 2002) and deeply lobed in H. mexicanus n. sp. The arrangement of the uterus also differentiates these two species; while in H. danbrooksi the descending and ascending uterine loops often invade both sides of the body, in H. mexicanus n. sp. descending and ascending uterine loops form two lateral fields and rarely invade one another. Finally, the longitudinal uterine loops in the posterior end of the body are shorter in H. danbrooksi .

Haematoloechus mexicanus n. sp. (Figs. 10 & 11) Type host: Montezuma leopard frog Rana montezumae (=Northern leopard frog R. pipiens Schreber and R. montezumae of Caballero 1941). Type locality: Ci��naga de Lerma, Estado de Mexico, Mexico. Site of infection: Lungs Holotype: CNHE 10489 Paratypes: CNHE 10490, 10491, 10492. Etymology: Species name refers to Estado de Mexico, the province of the type locality. Other hosts and localities: Mexico: Montezuma leopard frog Rana montezumae, Xochimilco, Mexico City (Caballero, 1941, as H. medioplexus); Patzcuaro leopard frog R. dunni, P��tzcuaro, Michoac��n (Le��n-R��gagnon et al. 1999, as H. coloradensis); Transverse Volcanic leopard frog R. neovolcanica, Cointzio, Michoac��n (this study). Description: Based on 17 mature specimens: Body slender, with thinner anterior region; 4.8���8.3 (7.0) mm long, 0.7���1.3 (1.0) mm of maximum width at testicular region. Tegument covered with abundant thin spines, easily lost during fixation; 7.5���12.5 (9.8) long. Oral sucker subterminal, round, 203���350 (284) long, 180���380 (278) wide. Pharynx oval, 140���280 (206) long, 122���220 (183) wide; oral sucker/pharynx ratio 1: 0.74���0.90 (0.83). Anterior border of pharynx and esophagus surrounded by gland cells. Esophagus 41���200 (129) long. Ceca bifurcated at 390���770 (609) from anterior extremity. Ceca terminate blindly near posterior extremity. Ventral sucker small, weakly developed, frequently obscured by uterus, 52���125 (82) long, 57���130 (84) wide, at 1.5���3.0 (2.4) mm (31%��� 41% (37%) of BL) from anterior extremity. Sucker length ratio 1:0.28���0.38 (0.33). Testes 2, elliptical, elongate, oblique, posterior to ovary; distance between ovary and anterior testis 350���825 (548). Anterior testis opposite to ovary, 365���1,080 (778) long, 243���600 (451) wide. Posterior testis 422���1200 (863) long, 260���830 (495) wide. Cirrus sac reaches anterior border of ventral sucker, mostly obscured by ascending uterus; internal seminal vesicle, elongate, slightly coiled. Ejaculatory duct weakly muscular, 150���160 (155) long, surrounded by prostatic gland cells. Ovary kidney shaped, lobed, 320���840 (623) long, 162���500 (342) wide; at 1.8���4.3 (2.8) mm (35%���57% (40%) of BL) from anterior extremity. Seminal receptacle posterior, partially overlapped with ovary; 300���1000 (644) long, 250���590 (410) wide. Mehlis gland dorsal to seminal receptacle. Laurer���s canal not observed. Vitellaria in clusters of oval, well defined follicles, distributed laterally, dorsally invade space between ceca in anterior region of ovary and sometimes in post-testicular region. Anterior limit of distribution 982���3200 (1766) (19%���49% (25%) of BL) from anterior end. Follicles extend asymmetrically, to anterior region of posterior testis on ovarian side of body, and halfway between posterior testis and posterior end of body on side opposite to ovary. Uterine loops fill intra- and extracecal space, partially overlap testes and ovary. Descending part of uterus form several diagonal loops that frequently bend anteriorly or posteriorly and form short longitudinal extracecal loops on ovarian side of body. Uterus forms two longitudinal uterine loops on each side of posterior end of body that reach halfway between posterior end and posterior testis; one loop is frequently shorter. Ascending part of uterus forms diagonal loops on side opposite to ovary, frequently bends anteriorly or posteriorly to form longitudinal extracecal loops. Descending and ascending parts of uterus in two lateral fields rarely invade each other. Distal uterus fills intracecal preovarian region with diagonal loops. Genital pore median, ventral to middle region of pharynx. Eggs dark brown, 22���26 (24) long, 14���20 (17) wide. Excretory vesicle not observed. Excretory pore terminal. Remarks: Haematoloechus mexicanus n. sp. resembles those species of the genus possessing short longitudinal or diagonal uterine loops not reaching the posterior testis, namely H. aubriae, H. caballeroi, H. danbrooksi, H. fuelleborni, H. humboldtensis, H. illimis, H. kernensis, H. occidentalis n. sp., H. pukinensis, and H. veracruzanus n. sp. It also resembles those species with a ventral sucker less than half the size of the oral sucker, namely H. combesi Batchvarov & Bourgat, 1974, H. danbrooksi, H. darcheni Combes & Knoepffler, 1967, H. floedae, H. leonensis (Williams & Coker, 1967), H. medioplexus, H. meridionalis, H. nicolasi, H. ocellati Gassmann, 1975 and H. parviplexus (Table 2). This new species differs from H. caballeroi, H. fuelleborni, H. humboldtensis, H. illimis, H. kernensis, H. occidentalis n. sp., H. pukinensis, and H. veracruzanus n. sp. in the size of the ventral sucker compared to the oral sucker, which is smaller in H. mexicanus n. sp. (1: 0.5���1.0 in the other species vs 1: 0.33 in H. mexicanus n. sp.), and it differs from H. aubriae in the presence of ventral sucker, which is absent in that species. It also differs from H. aubriae, H. caballeroi, H. fuelleborni, H. humboldtensis, H. kernensis, H. occidentalis n. sp., H. pukinensis, and H. veracruzanus n. sp. in the shape of ovary and testes, which are oval in those species, while in H. mexicanus n. sp. the ovary is lobed and testes are elliptical or elongate. Haematoloechus mexicanus n. sp. differs from H. combesi, H. darcheni, H. floedae, H. leonensis, H. medioplexus, H. meridionalis, H. nicolasi, H. ocellati and H. parviplexus in the arrangement of the uterine loops. Haematoloechus medioplexus and H. meridionalis lack uterine longitudinal loops (Stafford, 1902; Le��n-Regagnon et al. 2001), in H. combesi, H. floedae and H. leonensis they reach the level of the ovary (Williams & Coker 1967; Batchvarov & Bourgat 1974; Le��n-R��gagnon et al. 2005), in H. darcheni and H. ocellati they reach the level of the anterior testis (Combes & Knoepffler 1967; Gassmann 1975), in H. nicolasi and H. parviplexus they reach the level of the posterior testis (Irwin 1929; Le��n-R��gagnon 2017), while in H. mexicanus n. sp. they reach halfway between the posterior testis and the posterior end. In this new species there are frequently several short longitudinal uterine loops in the posttesticular region and at the level of testes, which are absent in the other species. Haematoloechus mexicanus n. sp. most closely resembles H. danbrooksi in the size of the ventral sucker and the presence of short diagonal or longitudinal uterine loops in the posterior end of body, but differs from that species in the shape of the ovary, which is oval or slightly bi-lobed in some specimens (Le��n-R��gagnon & Paredes-Calder��n 2002) and deeply lobed in H. mexicanus n. sp. The arrangement of the uterus also differentiates these two species; while in H. danbrooksi the descending and ascending uterine loops often invade both sides of the body, in H. mexicanus n. sp. descending and ascending uterine loops form two lateral fields and rarely invade one another. Finally, the longitudinal uterine loops in the posterior end of the body are shorter in H. danbrooksi ., Published as part of Le��n-R��gagnon, Virginia & Topan, Janet, 2018, Taxonomic revision of species of Haematoloechus Looss, 1899 (Digenea: Plagiorchioidea), with molecular phylogenetic analysis and the description of three new species from Mexico, pp. 251-302 in Zootaxa 4526 (3) on pages 269-272, DOI: 10.11646/zootaxa.4526.3.1, http://zenodo.org/record/2611615, {"references":["Caballero, C. E. (1941) Trematodos de las ranas de la Cienaga de Lerma, Mex. I. Anales del Instituto de Biologia de la Universidad Nacional Autonoma de Mexico, 12, 623 - 641.","Leon-Regagnon, V., Brooks D. R. & Perez-Ponce de Leon, G. (1999) Differentiation of Mexican species of Haematoloechus Loss, 1989 (Digenea: Plagiorchiformes): molecular and morphological evidence. Journal of Parasitology, 85, 935 - 946. https: // doi. org / 10.2307 / 3285832","Batchvarov, G. & Bourgat, R. (1974) Haematoloechus combesi n. sp. (Trematoda, Haematoloechidae), Parasite d' amphibiens anoures au Togo. Annales de Parasitologie Humaine et Comparee, 49, 337 - 342. https: // doi. org / 10.1051 / parasite / 1974493337","Combes, C. & Knoepffler, P. (1967) Parasites d'amphibiens du Gabon Haematoloechidae (Digenea). Biologia Gabonica, 3, 141 - 147.","Williams, M. O. & Coker, M. R. (1967) Two new trematodes from Petropedates natator Boulenger, in Sierra Leone. Journal of Helminthology, 16, 277 - 284. https: // doi. org / 10.1017 / S 0022149 X 00021660","Gassmann, M. (1975) Contribution a l'etude des trematodes d'amphibiens du Cameroun. Annales de Parasitologie, 50, 559 - 577. https: // doi. org / 10.1051 / parasite / 1975505559","Stafford, J. (1902) The American representatives of Distomum cygnoides. Zoologische Jahrbuecher Abteilung fuer Systematik Oekologie und Geographie der Tiere, 17, 411 - 424.","Leon-Regagnon, V., Brooks, D. R. & Zelmer, D. A. (2001) Morphological and molecular description of Haematoloechus meridionalis n. sp. (Digenea: Plagiorchioidea: Haematoloechidae) from Rana vaillanti Brocchi of Guanacaste, Costa Rica. Journal of Parasitology, 87, 1423 - 1427. https: // doi. org / 10.1645 / 0022 - 3395 (2001) 087 [1423: MAMDOH] 2.0. CO; 2","Leon-Regagnon, V., Guillen-Hernandez, S. & Arizmendi-Espinosa, M. A. (2005) Intraspecific variation of Haematoloechus floedae Harwood, 1932 (Digenea: Plagiorchiidae), from Rana spp. in North and Central America. Journal of Parasitology, 91, 915 - 921. https: // doi. org / 10.1645 / GE- 430 R. 1","Irwin, M. S. (1929) A new lung fluke from Rana clamitans Latreille. Transactions of the American Microscopical Society, 48, 74 - 79. https: // doi. org / 10.2307 / 3222463","Leon-Regagnon, V. & Paredes-Calderon, E. L. (2002) Haematoloechus danbrooksi n. sp. (Digenea: Plagiorchioidea) from Rana vaillanti from Los Tuxtlas, Veracruz, Mexico. Journal of Parasitology, 88, 1215 - 1221. https: // doi. org / 10.1645 / 0022 - 3395 (2002) 088 [1215: HDNSDP] 2.0. CO; 2"]}