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Elasmobranch populations are in steep decline mainly due to overfishing bycatch, but parasites may accelerate the collapse of vulnerable and/or highly parasitized species. We therefore studied metazoan parasites of Rajidae from the northeast Atlantic: vulnerable Leucoraja fullonica, near-threatened Raja brachyura, Raja clavata, Raja microocellata and Raja undulata, and least-concerned Raja montagui and Leucoraja naevus. Overall prevalence varied from 19% for R. montagui to 100% for L. fullonica. Parasite communities differed between skate species, and prevalence and abundance were higher for L. fullonica, R. microocellata, and R. undulata. We recorded 11 parasite taxa in the study: three nematodes, six cestodes, one monogenean, and one myxosporean. Whatever the skate species, the parasite component community comprised at least two nematode taxa among Phocanema spp., Proleptus sp. and Anisakis simplex. DNA-sequencing revealed that Phocanema azarasi and Phocanema krabbei both occurred in R. microocellata and R. undulata. Phocanema spp. was first recorded in L. fullonica, L. naevus, R. microocellata, R. montagui, and R. undulata, as Proleptus sp. in L. fullonica, and A. simplex in L. fullonica and R. clavata, Rockacestus sp. and Nybelinia sp. in R. undulata, and gill-myxosporeans on L. fullonica, L. naevus, R. microocellata, and R. undulata. The occurrence of 16 new host-parasite associations suggests potential environmental changes. Information provided by trophically transmitted helminths confirmed an opportunistic skate diet based on crustaceans and fish. We discuss results in terms of host fitness loss, bioindicator role of parasites, and anisakiasis risk. We recommend incorporating parasitology in research to improve elasmobranch conservation., (© 2024 The Author(s). Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

Troglocephalinae n. subfam. is proposed for Spinuris Doran, 1953, Neoheterocotyle Hargis, 1955, Anoplocotyloides Young, 1967, Troglocephalus rhinobatidis Young, 1967 (previously incertae sedis), Nonacotyle pristis Ogawa, 1991, Mehracotyle insolita Neifar, Euzet & Ben Hassine, 2002, Scuticotyle cairae n. gen. et sp., and Brancheocotyle imbricata n. gen. et sp. All members of the proposed new subfamily are gill parasites of shovelnose rays of the order Rhinopristiformes. The subfamilies Heterocotylinae Chisholm, Wheeler & Beverley-Burton, 1995, and Dasybatotreminae Bychowsky, 1957, are amended to exclude Spinuris, Nonacotyle, Neoheterocotyle, and Anoplocotyloides and Mehracotyle, respectively. Heterocotylinae includes gill parasites of members of the orders Myliobatiformes and Torpediniformes. Dasybatotreminae includes parasites of the gills and pharyngeal cavity of members of the orders Myliobatiformes and Rajiformes. A revised phylogeny of the Monocotylidae Taschenberg, 1879 is presented and discussed, based on 28S rDNA sequences, including new sequences for Myliocotyle pteromylaei Neifer, Euzet & Ben Hassine, 1999, Heterocotyle tokoloshei Vaughan & Chisholm, 2010, Neoheterocotyle robii Vaughan & Chisholm, 2010, and the two newly proposed species and genera. Additional locality records are also provided for Monocotylidae from off South Africa., (© 2024. The Author(s).)

The rhinebothriidean tapeworm family Escherbothriidae has recently been expanded to include the genus Ivanovcestus , species of which parasitise arhynchobatid skates. Similarities in morphology and host associations between Ivanovcestus and Semiorbiseptum - a genus yet to be assigned to one of the families in the order Rhinebothriidea - led us to explore the possibility that Semiorbiseptum might also belong in the Escherbothriidae. Morphological similarities with Scalithrium ivanovae , Scalithrium kirchneri and Rhinebothrium scobinae , all of which also parasitise arhynchobatid skates, raised questions regarding the generic placements of these species. In addition, new collections from the skate Sympterygia brevicaudata revealed two new species that morphologically resemble species of Ivanovcestus . A combination of morphological and molecular data were used to assess the generic placement of the newly discovered species and refine our understanding of the membership of the family Escherbothriidae. Sequence data for the D1-D3 region of the 28S rDNA gene were generated de novo for 14 specimens of 7 rhinebothriidean species and combined with comparable published data to represent all 6 families in the Rhinebothriidea in the analysis. The phylogenetic tree resulting from maximum likelihood analysis strongly supports the inclusion of the genus Semiorbiseptum in the family Escherbothriidae. Our work also suggests that the skate-hosted species previously assigned to Scalithrium and Rhinebothrium are also members of Semiorbiseptum and that Ivanovcestus is a junior synonym of Semiorbiseptum . Six species are transferred to Semiorbiseptum , bringing the total number of species in the genus to ten. The diagnosis of Semiorbiseptum is amended to accommodate the additional species. A second species in the previously monotypic type genus of the family, Escherbothrium , is described. The diagnosis of the Escherbothriidae is amended to include the new and transferred species. This study underscores the importance of integrating morphological and molecular data in bringing resolution to cestode systematics. We believe our findings provide a robust foundation for future research into the evolutionary history and host associations of cestodes within the order Rhinebothriidea and beyond. These also highlight the importance of expanding our understanding of skate-hosted cestodes. ZooBank: urn:lsid:zoobank.org:pub:8052AFCA-5FBD-4430-95F4-0E5E368DEA3D.

The parasites of hosts of conservation concern are often poorly known. This is the case with the iconic group of elasmobranchs known as the sawfish of the genus Pristis, all four species of which are considered as Endangered or Critically Endangered by the International Union for Conservation of Nature (IUCN, Switzerland). Examination of cestodes from three species of sawfish (Pristis pristis, Pristis clavata, and Pristis zijsron) in Australia and one of their close relatives, the also critically endangered widenose guitarfish, Glaucostegus obtusus, in India, collected over the past 25 years, yielded four new species of tapeworms which are described herein. All four belong to the previously monotypic Mixobothrium; the diagnosis of the genus is revised to accommodate the new species. Among the new taxa is a species that had been included in previous molecular phylogenies but whose identity and affinities within the order Rhinebothriidea, and thus also its familial placement, were unclear. This species exhibits the morphological features of Mixobothrium and thus its identity is, at long last, revealed. Sequence data generated for the 28S rDNA gene for three of the new species, as well as an additional new but yet undescribed species from Pristis pectinata from Florida (USA), confirms the uniqueness of this group among the rhinebothriideans. The new family Mixobothriidae is established to house these taxa. The members of this family differ from all but one of the five other families of rhinebothriideans in lacking apical suckers on their bothridia. They are also distinctive in that their bothridia are divided into three regions. The anterior and posterior regions have similar locular configurations to one another and differ from the locular configuration of the middle region. As a consequence, the bothridia are symmetrical along both their vertical and horizontal axes. We predict that a focus on species of guitarfish in the genus Glaucostegus will be the most productive approach for discovering additional diversity in this family of cestodes., (Copyright © 2023 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.)

Rajonchocotyle Cerfontaine, 1899, species are blood-feeding parasites on the gills of rajiforms. Eight species are considered valid, the most recent of which was described just after World War II. Many of the original descriptions of Rajonchocotyle species are limited in diagnostic value, and comparative museum material is scanty. The genus requires revision, and in support thereof, we provide detailed redescriptions for Rajonchocotyle albaCerfontaine, 1899, from the type host Rostroraja alba (Lacepède, 1803) and Rajonchocotyle emarginata (Olsson, 1876), Sproston, 1946, from 2 new host records, Raja straeleni Poll, 1951, and Leucoraja wallacei (Hulley, 1970), from South Africa, a new locality record. The generic diagnosis for Rajonchocotyle is amended to include greater details of the male reproductive system and confirms Paul Cerfontaine's and Nora Sproston's historic observations of the morphology of the male copulatory organ consisting of a separate proximal seminal vesicle and a distal cirrus. The lectotype of Rajonchocotyle kenojeiYamaguti, 1938, is assigned, and a comprehensive Rajonchocotyle-host species list is provided, highlighting species records that require further verification, and the purported global host range of R. emarginata is discussed., (© American Society of Parasitologists 2023.)

Peruanocotyle pelagica n. sp. is described based on specimens collected from the wall of the pharyngeal cavity of the Pacific cownose ray Rhinoptera steindachneri offshore Oaxaca and Guerrero, Mexico. The new species is distinguished from Peruanocotyle chisholmae by its anchors, which include a slender guard that curves towards the tip of the blade and which lack an accessory piece, morphological differences of the seminal vesicle, the lack of a male copulatory organ accessory piece and a greater number of spines, and an unsclerotized vagina. Molecular data of Peruanocotyle pelagica were generated to place the phylogenetic position of the genus within Monocotylidae., (© American Society of Parasitologists 2022.)

An emended diagnosis of ThaumatocotyleScott, 1904 (Monogenoidea: Monocotylidae) and a list of its species are provided. Merizocotyle urolophiChisholm and Whittington, 1999, Merizocotyle macrostrobusChisholm and Whittington, 2012, Merizocotyle papillaeChisholm and Whittington, 2012, and Merizocotyle rhadinopeosChisholm and Whittington, 2012 are transferred to Thaumatocotyle as new combinations. Thaumatocotyle pseudodasybatisHargis, 1955 is redescribed and is currently restricted to Thaumatocotyle-like helminths parasitizing the olfactory organs of the white-spotted eagle ray Aetobatus narinari (Euphrasen, 1790) (Myliobatiformes: Aetobatidae) in the western Atlantic Ocean. Two new species are described that infect the olfactory organs of pelagic eagle rays: Thaumatocotyle adelpha n. sp. from the ocellated eagle ray Aetobatus ocellatus (Kuhl, 1823) in the central and western Pacific Ocean and Thaumatocotyle casigneta n. sp. from the Pacific eagle ray Aetobatus laticeps Gill, 1865 from the eastern Pacific Ocean off the western coast of Mexico. Based on comparative morphology, T. pseudodasybatis, T. adelpha, and T. casigneta appear to form a subgroup of species that developed secondarily within the genus., (© American Society of Parasitologists 2021.)

Eutetrarhynchus pacificus n. sp. is described from the spiral valve of Raja inornata Jordan & Gilbert off the coast of California, USA. The new species is distinguished from E. ruficollis (Eysenhardt, 1829) and E. leucomelanus (Shipley & Hornell, 1906) in having acraspedote rather than craspedote segments and a saccate rather than a branched uterus. It is distinguished from E. platycephali Palm, 2004 in lacking an enlarged hook in the eighth row of the basal armature and from E. beveridgei Schaeffner, 2013, which has a basal swelling and a distinctive basal armature. A partial redescription of E. ruficollis, the type-species of the genus, is provided based on available museum specimens, highlighting the need for a comprehensive redescription of this species to better define the characteristics of the genus. The presence of an undescribed species in museum collections is also noted. Based on the 28S ribosomal gene, the new species clustered with Dollfusiella in a molecular phylogenetic tree. The delimitation of Eutetrarhynchus and its relationship with Dollfusiella is discussed.

The lecanicephalidean cestodes parasitizing the spiral intestine of the endangered giant freshwater whipray, Urogymnus polylepis (Bleeker), are investigated for the first time. Eight host specimens were collected between 2002 and 2008 at 2 collecting sites off the eastern coast of Borneo: 6 from the Kinabatangan River (Malaysia) and 2 from a fish market in Tarakan (Indonesia). Two of these individuals were found to be infected with a total of 3 new species of TetragonocephalumShipley and Hornell, 1905. Tetragonocephalum georgei n. sp. and Tetragonocephalum opimum n. sp. were recovered from a host specimen from the Kinabatangan River, and Tetragonocephalum levicorpum n. sp. was found parasitizing a host specimen purchased at a fish market in Tarakan. Specimens of each of the new species were prepared for light microscopy; specimens of 2 of the new species were prepared for scanning electron microscopy, and histological sections were prepared for 1 of the new species. The 3 new species are distinct from the 9 valid species of Tetragonocephalum and the 1 species inquirendum based on, for example, total length, number of proglottids and testes, and size of the scolex and acetabula. Tetragonocephalum georgei n. sp. and T. levicorpum n. sp. are unusual among their congeners in that they are euapolytic (i.e., gravid proglottids were not observed) rather than apolytic. They differ from one another in scolex and acetabula size. Tetragonocephalum opimum n. sp. is unusual among its congeners in its possession of vitelline follicles arranged in 2, rather than 3, regions in the proglottid. These new species increase the total number of valid species of Tetragonocephalum to 12 and the total number of known cestodes from U. polylepis to 13 species across 6 genera in 4 orders. This is the first account of lecanicephalideans reported from freshwater. The taxonomic status of each of the 32 nominal taxa historically associated with Tetragonocephalum is re-assessed. Type host identities of all valid species are revised and discussed in light of recent taxonomic efforts in the Dasyatidae Jordan and Gilbert., (© American Society of Parasitologists 2021.)

The examination of eight spotted skates, Raja straeleni Poll, resulted in the discovery of four new species of Acanthobothrium van Beneden, 1849, namely A. microhabentes sp. n., A. microtenuis sp. n., A. crassus sp. n., and A. dolichocollum sp. n., located off the Western Cape of South Africa. With a total of over 200 valid species of Acanthobothrium recognised worldwide, the use of an integrative approach becomes imperative in the interest of simplifying interspecific comparisons between congeners. In accordance with this, the four new species were incorporated into the category classification system established by Ghoshroy and Caira in 2001, where they were identified as category 2 species, which, at present, includes 47 recognised species of Acanthobothrium. Nevertheless, each of the four new species exhibits postovarian testes, a most intriguing and highly unusual feature among Acanthobothrium, instantly differentiating them from most congeners. This feature has been reported in 12 congeners, which have previously been considered to be restricted to waters of the Indo-Pacific Ocean. Not only do the four new congeners represent the first species of Acanthobothrium reported from southern Africa, but they also represent the first reported species with postovarian testes from the southern Atlantic Ocean. Regarding the legitimacy of the four new species, only two other category 2 species are reported to exhibit this feature, namely A. popi Fyler, Caira et Jensen, 2009, and A. bobconniorum Fyler et Caira, 2010, to which the four congeners were compared to. Acanthobothrium microhabentes sp. n. is the smallest of the congeners and differs from A. popi and A. bobconniorum by having fewer testes and postovarian testes, a shorter body, fewer proglottids, a shorter scolex, and longer cephalic peduncle. Acanthobothrium microtenuis sp. n. differs from A. popi and A. bobconniorum by having fewer testes and postovarian testes, a shorter scolex, longer cephalic peduncle, and the possession of columnar spinitriches on the anterior region of the terminal proglottid. Acanthobothrium crassus sp.n. differs from A. popi and A. bobconniorum by having fewer postovarian testes, a narrower cirrus-sac, larger vitelline follicles, and a longer cephalic peduncle. Acanthobothrium dolichocollum sp. n. is the longest of the four new species and differs from A. popi and A. bobconniorum by having fewer postovarian testes, more postporal testes, a larger body, more proglottids, larger testes and vitelline follicles, and an exceptionally long cephalic peduncle. Apart from differences in overall size, the four new species differ in a combination of measurements for the scolex, vitelline follicles, muscular pad and cephalic peduncle, and the number of proglottids and testes. The four species were recovered from a previously unexplored host and locality, expanding the host associations and geographical distribution of the genus.

Heterocotyle whittingtoni n. sp. (Monogenea: Monocotylidae) is described from the gills of the black-spotted whipray Maculabatis toshi (Whitley) (Dasyatidae) collected from Moreton Bay near Dunwich and Peel Island, and from the eastern Gulf of Carpentaria off Weipa, Queensland, Australia. Heterocotyle whittingtoni n. sp. has a single sinuous ridge surmounting the haptoral septa and the male copulatory organ lacks an accessory piece. The new species can be distinguished from the two other Heterocotyle species that have this combination of characters by the distal portion of the male copulatory organ which is slightly flared with uniquely thickened walls and by the morphology of the testis. The identity of the host of H. whittingtoni n. sp. is discussed. We confirm that the host of the monocotylids Dendromonocotyle lasti Chisholm & Whittington, 2005 and Monocotyle caseyae Chisholm & Whittington, 2005 originally identified as "Himantura sp." was M. toshi.

Eighteen monocotylid species were collected from elasmobranchs during surveys of the parasites of fishes of Moreton Bay, Queensland, Australia. Two new species, Calicotyle cutmorei n. sp. (Calicotylinae) from Carcharhinus sorrah (Valenciennes) (Carcharhiniformes) and Dendromonocotyle raiae n. sp. (Monocotylinae) from Hemitrygon fluviorum (Ogilby) and Neotrygon trigonoides (Castelnau) (both Myliobatiformes) are described and illustrated. Six new faunal records for Moreton Bay are reported: Thaumatocotyle australensis Beverley-Burton & Williams, 1989 (Merizocotylinae) from Maculabatis toshi (Whitley) (Myliobatiformes); Monocotyle corali Chisholm, 1998 (Monocotylinae) from Pastinachus ater (Macleay) (Myliobatiformes); Neoheterocotyle rhynchobatis (Tripathi, 1959) Chisholm, 1994 (Heterocotylinae) from Glaucostegus typus (Anonymous [Bennett]) and Aptychotrema rostrata (Shaw) (both Rhinopristiformes); and Decacotyle elpora Marie & Justine, 2005 (Decacotylinae), Dendromonocotyle torosa Chisholm & Whittington, 2004 (Monocotylinae), and Clemacotyle australis Young, 1967 (Monocotylinae) from Aetobatus ocellatus (Kuhl) (Myliobatiformes). Maculabatis toshi is a new host record for T. australensis, and A. rostrata is a new host record for N. rhynchobatis. Ten species previously recorded from Moreton Bay were collected: Monocotyle caseyae Chisholm & Whittington, 2005 (Monocotylinae) and Heterocotyle whittingtoni Chisholm & Kritsky, 2020 (Heterocotylinae) from M. toshi; Monocotyle sp. A of Chisholm (1998a) (Monocotylinae) from H. fluviorum; Dendromonocotyle kuhlii Young, 1967 and Monocotyle kuhlii Young, 1967 (both Monocotylinae) from N. trigonoides; Thaumatocotyle cf. pseudodasybatis Hargis, 1955 (Merizocotylinae), Empruthotrema kearni Whittington, 1990 (Merizocotylinae) and Decacotyle octona Young, 1967 (Decacotylinae) from A. ocellatus; and Mycteronastes icopae (Beverley-Burton & Williams, 1989) Kearn & Beverley-Burton, 1990 (Merizocotylinae) and Troglocephalus rhinobatidis Young, 1967 (Dasybatotreminae) from G. typus.

Here we describe a new species of RhinebothriumLinton, 1890, from Hypanus guttatus (Bloch and Schneider). Rhinebothrium ramosi n. sp. can be differentiated from all 51 valid species of the genus by having 4-5 testes and uterus that extends throughout the entire length of the proglottid. Only 8 of the above species closely resemble R. ramosi in total length (Rhinebothrium bunburyense, Rhinebothrium chollaense, Rhinebothrium corbatai, Rhinebothrium dasyatidis, Rhinebothrium kruppi, Rhinebothrium lintoni, Rhinebothrium margaritense, and Rhinebothrium reydai). Despite the resemblance, R. bunburyense, R. corbatai, R. dasyatidis, R. lintoni, and R. margaritense can be distinguished from the new species by possessing a larger number of proglottids. The remaining 3 species (R. chollaense, R. kruppi, and R. reydai) overlap in total length and number of proglottids with R. ramosi. However, they can be distinguished from the new species by possessing a single posterior-most bothridial loculus instead of arranged as a pair, as found in the new species. This is the first report of the genus from the coastal waters of Brazil and brings to 52 the number of valid species for this genus. Additionally, we use the patterns of infection and distribution for species of Rhinebothrium to make predictions of expected diversity within the genus, especially for unsurveyed hosts in endemic marine ecoregions of the world., (© American Society of Parasitologists 2020.)

Examination of 4 specimens of the leopard whipray Himantura leoparda, a dasyatid stingray from northern Australia, led to the discovery of 3 new species of Rhinebothrium. Rhinebothrium leopardensis n. sp., Rhinebothrium nandoi n. sp., and Rhinebothrium ruhnkei n. sp. are described, increasing the diversity of the genus to 51 species globally. All 3 new species differ from their congeners in terms of testis number, proglottid number, loculus number, and size. With respect to one another, R. leopardensis n. sp. has bothridia that are weakly constricted at their centers and has a greater number of proglottids than the other 2 species (93-108 vs. 11-15, and 48-78, respectively). Rhinebothrium nandoi n. sp. is the smallest of the 3 species found in H. leoparda (3.6-5 vs. 10-15 mm and 10.1-15.8 mm in total length [TL], respectively) and bears bothridia that are constricted at their centers. Rhinebothrium ruhnkei n. sp. bears bothridia that are conspicuously constricted at their centers and has more testes than R. leopardensis and fewer than R. nandoi (7-10 vs. fewer than 7 and 21-33, respectively). Before this study, 56% (27 of 48) of Rhinebothrium species had been described from the freshwater river systems of South America and the marine waters surrounding South and North America. In contrast, despite the remarkably diverse nature of its batoid fauna, only 19 species were known from the Indo-Pacific region. Our work increases this number to 22, emphasizing the highly underestimated nature of Rhinebothrium diversity in this region of the globe. The discovery of these 3 new species was not unexpected, given the relatively poor status of our current knowledge of the cestode faunas of dasyatid stingrays in the Indo-Pacific region, and given the fact that it is common for a single batoid species to host 2 or more species of Rhinebothrium. Our results suggest that additional work on the cestode faunas of the batoids, especially dasyatids, from the Indo-Pacific region is likely to be highly productive in terms of contributing to the knowledge of Rhinebothrium diversity., (© American Society of Parasitologists 2020.)

Introduction: A new monogenean, Heterocotyle margaritae n. sp. (Monocotylidae: Heterocotylinae), is described based on specimens collected from the gills of the diamond stingray, Hypanus dipterurus (Jordan & Gilbert, 1880) (Myliobatiformes: Dasyatidae) captured off the South Pacific coast, Lima Region, Peru., Materials and Methods: Monogeneans were fixed in hot 4% formalin, observed and measured as permanent mounts stained with Gomori's trichrome, and mounted in Canada balsam. Drawings were made with the aid of a drawing tube., Results: The new species is distinguished from all congeners mainly by having a funnel-shaped male copulatory organ, spatulate distally with lateral folds and by its club-shaped accessory piece. The most similar congener, H. americana Hargis, 1955, resemble H. margaritae n. sp. regarding the general structure of the male copulatory organ (funnel-shaped with an accessory piece). However, besides other features, the new species differ from H. americana by having an accessory piece without a dorsal button (vs an accessory piece with a dorsal button in H. americana)., Conclusions: This is the first report of a member of Heterocotyle Scott, 1904 in the Southeastern Pacific Ocean. The present finding brings to 20 the number of known species of Heterocotyle, and represents the fifth described monogenean species from Hypanus dipterurus.

Kabata separated species of Pseudocharopinus Kabata, 1964 and Charopinus Krøyer, 1863 in 1964 based mainly on four characteristics. Currently Pseudocharopinus has 11 species while Charopinus consists of three species considered valid. Pseudocharopinus malleus (Rudolphi in Nordmann, 1832) and Charopinus dubius T. Scott, 1900 were collected and studied from hosts off South Africa. Additional to previous reports from South African waters, P. malleus is reported from Torpedo sinuspersici Olfers and T. fuscomaculata Peters while C. dubius is reported from Leucoraja wallacei (Hulley) and Rajella dissimilis (Hulley), all new host records. In an attempt to estimate the evolutionary relationships among Pseudocharopinus spp. a cladistic analysis was performed by means of parsimony using described and illustrated features of the adult females. Due to the mostly unresolved 50% majority rule tree, a key for the identification of the adult females of Pseudocharopinus spp. is compiled. Additionally, a key for the identification of adult females of Charopinus spp. is provided.

Introduction: Specimens of Rhinobatonchocotyle pacifica Oliva & Luque, 1995 (Hexabothriidae) were collected from the gill filaments of Pacific guitarfish, Pseudobatos planiceps (Garman, 1880) (Rhinopristiformes: Rhinobatidae), from off the coast of Chorrillos, Lima, Peru. Since the original description of R. pacifica was incomplete, we herein redescribe R. pacifica based on re-examination of the holotype, paratypes, and newly collected voucher specimens. Nucleotide sequences (18S, 28S) for R. pacifica are presented for the first time, and a phylogenetic analysis conducted., Materials and Methods: Monogeneans were examined with light microscopy and partial sequences of 18S and 28S rDNA genes were obtained., Results: The following taxonomically important morphological features are described: presence of seminal receptacle, spiniform papillae within oral cavity, haptoral sucker sclerites and anchors, hook surface striations, muscular pad associated with each haptoral sucker sclerite (except sclerite 1), muscular bulbs in appendix suckers, and oötype lacking longitudinal rows of large cells (oötype not côtelé). The genital complex is detailed. The diagnosis of Rhinobatonchocotyle is emended to include species with or without seminal receptacle. Representative nucleotide sequences of partial 18S and 28S rDNA genes of R. pacifica were obtained for the first time and used for reconstructing the phylogeny of Hexabothriidae., Conclusion: The phylogenetic reconstruction confirmed the species within the Hexabothriidae.

During an extensive research project involving 519 specimens of batoids, including 13 species of Rajiformes and Myliobatiformes (Chondrichthyes) from the Argentine Sea, three new species of Empruthotrema were found and are described using morphologic characteristics and two molecular markers: LSU rDNA and COI mtDNA. The new species can be distinguished from their congeners by the number and distribution of the marginal loculi, the length and morphology of male copulatory organ, and the presence of eyespots. Additionally, multivariate analysis identified the dimensions of the pharynx and ejaculatory bulb as diagnostic features. Host specificity and previous records of the genus in the region are discussed. This is the first description of new species in this genus for the Southwestern Atlantic Ocean, as well as for arhynchobatid hosts.

An understanding of the mechanisms that determine host and parasite relationships is a central aim in parasitology. Association of a parasite species with a host species may be influenced primarily by phylogenetic constraints that cause parasite species to co-speciate with their host species, or predominantly by ecological parameters that influence all other co-evolutionary scenarios. This study aimed to investigate the role of co-speciation as well as other co-evolutionary scenarios in influencing the assemblages of tapeworm parasites (marine cestodes) in skate hosts (Rajiformes) using a modification of the PACo (Procrustean Approach to Cophylogeny) method. The study found that phylogeny and host ecology are both significant predictors of skate-tapeworm relationships, implying that co-speciation as well as other co-evolutionary scenarios are shaping these associations. The study also investigated the key ecological parameters influencing host-switching and found that host diet, distribution depth, average body size and geographical location have a combined effect. Given the importance of parasites in ensuring healthy and stable marine ecosystems, the findings of this study have implications for conservation management worldwide.

Background: Parasites of deep-sea fishes from the South-East Pacific (SPO) are poorly known. Of c.1030 species of fish found in this area, 100-150 inhabit the deep-sea (deeper than 200 m). Only six articles concerning metazoan parasites of fish from deep-waters of SOP are known, and nine monogenean species have been reported. Currently, ten species are known in Acanthocotyle Monticelli, 1888 (Monogenea) and when stated, all of them are found in shallow waters (10-100 m). Acanthocotyle gurgesiella Ñacari, Sepulveda, Escribano & Oliva, 2018 is the only known species parasitizing deep-sea skates (350-450 m) in the SPO. The aim of this study was the description of two new species of Acanthocotyle from two Rajiformes., Methods: In September 2017, we examined specimens of two species of deep-sea skates (Rajiformes), Amblyraja frerichsi (Krefft) and Bathyraja peruana McEachran & Myyake, caught at c.1500 m depth off Tocopilla, northern Chile, as a by-catch of the Patagonian tooth fish Dissostichus eleginoides Smitt fishery. Specimens of Acanthocotyle were collected from the skin of the skates. Morphometric (including multivariate analysis of proportional measurements, standardized by total length), morphological and molecular analyses (LSU rRNA and cox1 genes) were performed in order to identify the collected specimens., Results: The three approaches used in this study strongly suggest the presence of two new species in the genus Acanthocotyle: Acanthocotyle imo n. sp. and Acanthocotyle atacamensis n. sp. parasitizing the skin of the thickbody skate Amblyraja frerichsi and the Peruvian skate Bathyraja peruana, respectively. The main morphological differences from the closely related species Acanthocotyle verrilli Goto, 1899 include the number of radial rows of sclerites, the non-discrete vitelline follicles and the number of testes., Conclusions: The two species of monogeneans described here are the only recorded parasites from their respective host species in the SPO. Assessing host specificity for members of Acanthocotyle requires clarifying the systematics of Rajiformes.

Examination of rajid skates off the Algerian coast in the Mediterranean Sea revealed that three of the 33 Dipturus batis Linnaeus, 1758 examined harboured a new tapeworm species: Echeneibothrium algeriensis n. sp. This new species, collected from the anterior half of the spiral valves, is described on the basis of morphological data from light and scanning electron microscopy. The new species differs from previously described Echeneibothrium species by details of the scolex and loculi, total length, the length of the myzorhynchus, the number of proglottides, and the number of testes. Comparison of the diets of the ten skate species common in the Mediterranean basin indicates some varying degree of overlap, suggesting that host specificity in this host-parasite system is determined by other host and/or ecological variables such as adaptations of the parasites to their respective hosts, either on the morpho-anatomical level, in physiological characteristics of the parasite's habitat, in the trophic requirements for the successful transmission of the parasite, or in adaptations to the behavioural characteristics of the host. Furthermore, restricted overlap of E. algeriensis n. sp. with congeners in parasite assemblages of D. batis indicates some structuring according to attachment-site preferences. However, attachment-site preferences are not explained solely by morphological compatibility between bothridia and villi. This study reiterates the need to examine multiple factors synergistically in studies on host specificity of parasites, and the need to examine the parasite fauna of hosts across their entire geographical range in order to truly appreciate the biodiversity they harbour.

There are limited reports of infectious agents affecting Australian cowtail stingrays. In the present study, a new species of ascaridoid nematode belonging to the genus Mawsonascaris is described. The most distinct characteristic features were observed in females (the presence of a polar spine in the eggs and a flap-like projection in the vulval area). An identification key for Mawsonascaris spp. is provided. Additionally, internal transcribed spacers (ITS) sequences were obtained for the new species. Alignment of the ITS sequence of the specimens in the present study with those deposited in GenBank showed that there exists no other highly similar sequence. Phylogenetic analyses resulted in a distinct grouping of our specimens supporting morphological distinction from previously described Mawsonascaris spp. Histology was used to investigate the pathology caused by the infection. Necrosis, inflammation and fibrosis were evident at the border of the nodules formed by parasite. A large number of parasites were present in muscularis mucosae and submucosa but not in the muscularis of the stomach. The parasites were associated with an increased inflammatory response, which was also found in the muscularis mucosae and submucosa. Similar pathology has been described in elasmobranchs infected by cestodes, although with more severe lesions., (© 2019 John Wiley & Sons Ltd.)

Collections of rhinebothriidean cestodes (Platyhelminthes) from Australian batoid elasmobranchs revealed the presence of a number of new genera and species. Ruptobothrium louiseuzeti n. g., n sp. is described from the reticulate whipray, Himantura australis Last, Naylor & Manjaji-Matsumoto, from off the Northern Territory and Mixobothrium queenslandense n. g., n sp. is described from the green sawfish, Pristis zijsron Bleeker, from off north-eastern Queensland. Two new species of Rhabdotobothrium Euzet, 1953 are described: Rhabdotobothrium meridionale n. sp. from the southern eagle ray Myliobatis tenuicaudatus Hector from off South Australia and Rhabdotobothrium anoxypristidis n. sp. from the narrow sawfish, Anoxypristis cuspidatus (Latham) from off north Western Australia. A new species of Scalithrium Healy & Reyda, 2016, Scalithrium australiense n. sp., is described from the reticulate whipray, Himantura australis Last, Naylor & Manjaji-Matsumoto, from off northern Western Australia. Scalithrium smitii (Shinde, Deshmukh & Jadhav, 1981) n. comb. is reported from Australian waters for the first time in the black spotted stingray Maculabatis toshi (Whitley) from off northern Western Australia. New host and geographical records are provided for Stillabothrium jeanfortiae Forti, Aprill & Reyda, 2016 from the brown whipray Maculobatis toshi (Whitley) and the black-spotted whipray, Maculabatis cf. astra (Last, Manjaji-Matsumoto & Pogonoski) from Moreton Bay in southern Queensland.

Parasites are important components of natural systems, and among their various roles, parasites strongly influence the flow of energy between and within food webs. Over 1000 tapeworm species are known to parasitise elasmobranchs, although full life cycles are resolved for fewer than 10 of them. The lack in resolution stems from the inability to distinguish larval from adult stages using morphology alone. Molecular elucidation of trophic transmission pathways is the next step in understanding the role of hosts and parasites within food webs. We investigated the parasite assemblage of New Zealand's rough skate, Zearaja nasuta. Skates and their prey items (obtained from the skates' stomachs) were dissected for the recovery of adult and larval tapeworms, respectively. A fragment of the 28S rDNA region was amplified for worm specimens with the aim to confirm species identity of parasites within rough skates and to uncover trophic transmission pathways that exploit the predation links between rough skates and their prey. We identified seven species of tapeworms from four tapeworm orders. Four trophic transmission pathways were resolved between three prey items from skates stomachs and skates, and one pathway between larval tapeworm sequence from a New Zealand sole and skate, i.e. a genetic match was found between larval tapeworms in prey and adult worms in skates. We report the first case of an adult trypanorhynch parasitising rough skate. These findings contribute to our limited understanding of cestode life cycles as well as providing insights into the importance of predator-prey relationships for parasite transmission.

Eighteen species of Dendromonocotyle Hargis, 1955 (Monogenea: Monocotylidae) have so far been described from elasmobranchs worldwide. In this paper, two new species are described; Dendromonocotyle tsutsumii n. sp. from the skin of the Japanese eagle ray, Myliobatis tobijei Bleeker from Tokyo Bay and the pitted stingray, Dasyatis matsubarai Miyosi, from Ooarai, Ibaraki Prefecture, Japan, and Dendromonocotyle fukushimaensis n. sp. from the skin of the cow stingray, Dasyatis ushiei (Jordan & Hubbs) reared at an aquarium in Fukushima Prefecture, Japan. Dendromonocotyle tsutsumii is distinguished from the congeners by the presence of a sclerotised duct connecting the vagina with the seminal receptacle, and De. fukushimaensis by the large body size and the presence of a donut-shaped structure encircling the male copulatory organ near its distal end. Additionally, the reproductive system of Dendromonocotyle akajeii Ho & Perkins, 1980 is redescribed, based on specimens from the skin of the whip stingray, Hemitrygon akajei (Müller & Henle) (syn. Dasyatis akajei) caught in Hamana Lake, Shizuoka Prefecture, Japan. A key to the 20 species of Dendromonocotyle including the present new species is provided.

Gymnurahemecus bulbosus gen. et sp. nov. infects the heart of smooth butterfly rays, Gymnura micrura in the Gulf of Mexico. Gymnurahemecus differs from all other accepted aporocotylid genera by having one column of C-shaped lateral tegumental spines, a medial oesophageal bulb anterior to a diverticulate region of the oesophagus, inverse U-shaped intestinal caeca, a non-looped testis, an oviducal ampulla, a Laurer's canal, and a post-caecal common genital pore. The new species, the shark blood flukes (Selachohemecus spp. and Hyperandrotrema spp.), and the chimaera blood fluke Chimaerohemecus trondheimensis are unique by having C-shaped lateral tegumental spines. Selachohemecus spp. and the new species have a single column of lateral tegumental spines, whereas Hyperandrotrema spp. and C. trondheimensis have 2-7 columns of lateral tegumental spines. The new species differs from Selachohemecus spp. most notably by having an inverse U-shaped intestine. The other ray blood flukes (Orchispirium heterovitellatum, Myliobaticola richardheardi, and Ogawaia glaucostegi) differ from the new species by lacking lateral tegumental spines, a medial oesophageal bulb, and a Laurer's canal and by having a looped testis. Phylogenetic analysis using large subunit ribosomal DNA (28S) indicated that the new species is sister to the clade that includes the other sequenced adult blood fluke (O. glaucostegi), which infects a ray in Australia. These results agree with and extend previous morphology- and nucleotide-based phylogenetic assertions that the blood flukes of early-branching jawed craniates (Chondrichthyes) are monophyletic and phylogenetically separated from the blood flukes of later-branching ray-finned fishes (Actinopterygii: Euteleostei).

Seven new species of the cestode genus Rhinebothrium Linton, 1890 are reported from the spiral intestines of batoid elasmobranchs from the coasts of Australia. The new species are: Rhinebothrium dasyatidis n. sp. from the smooth stingray Bathytoshia brevicaudata (Hutton) from Spencer Gulf, South Australia; Rhinebothrium bunburyense n. sp. from the southern eagle ray, Myliobatis tenuicaudatus Hector from off Bunbury, Western Australia; Rhinebothrium vandiemeni n. sp. from the reticulate whipray, Himantura australis Last, Naylor & Manjaji-Matsumoto from off Cape van Diemen, Northern Territory; Rhinebothrium fluviorum n. sp. from the estuary stingray, Hemitrygon fluviorum (Ogilby) from Moreton Bay, Queensland; Rhinebothrium urolophi n. sp. from the wide stingaree Urolophus expansus McCulloch from off Beachport, South Australia; Rhinebothrium nickoli n. sp. from the brown whipray Maculabatis toshi (Whitley) and the reticulate whipray, Himantura australis Last, Naylor & Manjaji-Matsumoto, from Nickol Bay, Western Australia and from the white-spotted guitarfish Rhynchobatus australiae (Whitley) from off Broome, Western Australia and Rhinebothrium fungiforme n. sp. from the estuary stingray, Hemitrygon fluviorum (Ogilby) from Fog Bay in the Northern Territory.

Species of the eutetrarhynchid genus Hispidorhynchus Schaeffner and Beveridge, 2012 possess an uncinate macrohook on the bothrial surface of the basal swelling of each tentacle. This unique feature of the oncotaxy is only shared with the closely related genus Oncomegas Dollfus, 1929 . A new species of Hispidorhynchus is described from specimens infecting Styracura schmardae (Werner, 1904) (Potamotrygonidae) from the western Caribbean Sea off the coast of Belize and Panama. Hispidorhynchus styracurae n. sp. differs from its 3 congeners in the possession of smaller and narrower bulbs, fewer principle hooks in the metabasal armature, size of the macrohook, and different scolex proportions. Scanning electron microscopy reveals new information on the microthrix morphology of the genus. A diagnostic key for the differentiation of species of Hispidorhynchus is provided. In addition, new host and locality records are reported for Oncomegas wageneri ( Linton, 1890 ) Dollfus, 1929 , collected from Hypanus guttatus (Bloch and Schneider, 1801) (Dasyatidae) off the coast of Maceió, Alagoas (Brazil). This considerably expands the geographical distribution of this species in the western Atlantic Ocean.

The spiral intestines of a total of 16 round fantail stingrays Taeniurops grabata from the Mediterranean Sea off Tunisia were examined for cestodes. A new genus is erected in the Anthocephaliidae (Rhinebothridea) as Alveobothrium gen. n., with Alveobothrium grabatum sp. n. as its type species; the new genus differs from the other genera in the order in that its members possess bothridia with an apical sucker, marginal loculi and multiple staggered rows of facial loculi. Alveobothrium zarzisense sp. n. is also described. The species differ in the number of marginal loculi and in proglotid anatomy. Another anthocephaliid belonging to the genus Anthocephalum is also described from T. grabata. Anthocephalum jeancadenati sp. n. is most similar to A. alicae and A. michaeli, but differs in size of terminal proglottid and number of proglottids. All these new species are also found in formalin-preserved cestodes from T. grabata collected at Gorée Island (Senegal) between 1946 and 1954 by the French ichthyologist J. Cadenat and conserved in the personal collection of the late L. Euzet. The presence of the same rhinebothriideans species parasitizing T. grabata in both the Mediterranean (Tunisia) and the eastern Atlantic (Senegal) is discussed.

Five new species of the elasmobranch tapeworm genus Anthocephalum Linton, 1890 (Rhinebothriidea: Anthocephaliidae Ruhnke, Caira and Cox, 2015 ) are described from the mangrove whipray, Urogymnus granulatus (Macleay) from the Solomon Islands and northern Australia. Anthocephalum blairi n. sp., Anthocephalum gravisi n. sp., Anthocephalum haroldsoni n. sp., Anthocephalum mounseyi n. sp., and Anthocephalum ruhnkei n. sp. differ from one another and their congeners based on quantitative and qualitative features of the scolex and proglottid anatomy. Species boundaries recognized by these distinguishing morphological features are supported by a maximum likelihood phylogenetic analysis based on combined 18S rDNA and 28S rDNA (D1-D3) sequence data showing the new species as independent lineages among 13 of the 18 species of Anthocephalum described to date. Several morphological features (the possession of columns of vitelline follicles that are interrupted by the ovary, a uterus that does not extend to the anterior margin of the proglottid but stops short in the anterior region of the field of testes, proximal surfaces of the marginal loculi covered with acicular filitriches only throughout, or with gladiate spinitriches and acicular filitriches throughout, and proximal bothridial surfaces with gladiate spinitriches and acicular filitriches) are collectively exhibited by the 5 new species and have not been documented previously in other species of Anthocephalum. The genus is herein amended to reflect these features. Additionally, the replacement name Anthocephalum centrurum ( Southwell, 1925 ) Ruhnke, 1994 is reinstated as the valid name for the type species of the genus, Anthocephalum gracile Linton, 1890 , with the latter being the junior secondary homonym of A. gracile ( Wedl, 1855 ) Ruhnke, 1994 . The description of these new species increases the number of valid species of Anthocephalum from 18 to 23.

Morphological and molecular analyses of cestode specimens collected during survey work of batoid elasmobranchs and their parasites in Senegal revealed two new species of the rhinebothriidean cestode genus Stillabothrium Healy et Reyda 2016. Stillabothrium allisonae Dedrick et Reyda sp. n. and Stillabothrium charlotteae Iwanyckyj, Dedrick et Reyda sp. n. are both described from Fontitrygon margaritella (Compagno et Roberts) and Fontitrygon margarita (Günther). Both new cestode species overlap in geographic distribution, host use and proglottid morphology, but are distinguished from each other, and from the other seven described species of Stillabothrium, on the basis of their pattern of bothridial loculi. Phylogenetic analyses based on sequence data for 1,084 bp from the D1-D3 region of 28S rDNA that included multiple specimens of both new species and eight other species of Stillabothrium corroborated the morphologically-determined species boundaries. The phylogenetic analyses indicate that S. allisonae sp. n. and S. charlotteae sp. n. are sister species, a noteworthy pattern given that the two species of the stingray genus Fontitrygon they both parasitise, F. margaritella and F. margarita, are also sister species. Although species of Stillabothrium vary widely in their patterns of facial loculi, the variation does not appear to correlate with phylogeny. Most species of Stillabothrium parasitise myliobatiform elasmobranch genera of the Dasyatidae Jordan. This study brings the number of described species of Stillabothrium to nine, three of which occur in the eastern Atlantic, two of which occur off the northern coast of Australia, and four of which are from coastal Borneo.

A new genus and species of monogenean belonging to Hexabothriidae, Hypanocotyle bullardi n. gen. n. sp., is described based on specimens collected from the gill filaments of the diamond stingray, Hypanus dipterurus (Jordan et Gilbert) (Myliobatiformes: Dasyatidae), a demersal chondrichthyan collected off the coast of Callao, Peru. Hypanocotyle n. gen. has the following combination of diagnostic features that differentiate it from other hexabothriid genera: haptor symmetrical; vasa efferentia having proximal (narrow, with thin glandular wall) and distal (expanded, interlaced, with thick glandular wall) portions, joining medially to form vas deferens; vas deferens having proximal (expanded, sinuous, with thick glandular wall) and distal (narrow, strongly sinuous, with thin glandular wall) portions; male copulatory organ unarmed, proximal portion slightly sinuous and tube-like, distal portion funnel-shaped; prostatic glands present, distributed around of the MCO; seminal receptacle present; ootype lacking longitudinal rows of large cells (no oötype côtelé); vaginae parallel, with well-differentiated proximal (glandular, narrow, tube-like, slightly sinuous) and distal (musculoglandular, convoluted) portions; gland cells surrounding the vaginal duct along the entire length of distal portion, densely clustered in middle portion; uterine eggs with 2 elongate filaments. Phylogenetic reconstructions by maximum-likelihood method, based on newly obtained partial 18S and 28S sequences, shows that H. bullardi n. gen. is included within the family Hexabothriidae, order Diclybothriidea. This is the second hexabothriid genus recorded from a diamond stingray (Dasyatidae), and the fourth hexabothriid species recorded from Peru. A key to hexabothriid genera is provided., (Copyright © 2018. Published by Elsevier B.V.)

Little is known about the diversity of parasites of the deep-sea fish of the world's oceans. Here, a new species of monogenean parasite of the deep-sea skate Gurgesiella furvescens is described. Specimens of parasites were obtained from the skin of two specimens of the dusky finless skate, G. furvescens (Rajidae), in the vicinity of Valparaiso (33°S, 72°W), central Chile, from midwater trawl fishing at depths of 350-450 m. Both morphological and molecular analyses were conducted to provide a full description of the new species, named Acanthocotyle gurgesiella. For the molecular analyses, nuclear large subunit (LSU) rDNA and the mitochondrial gene cytochrome c oxidase 1 (COI) were used. From the morphological analysis and a comparison with the known species of the genus, A. gurgesiella can be identified by a combination of morphological characteristics, including the number of testes, number of radial rows of sclerites in the pseudohaptor, aperture of the genital pore and shape of the vitelline follicles. The results from the DNA analysis indicated that A. gurgesiella has a genetic divergence of 3.2-3.7% (LSU rDNA gene) from A. urolophi, the only congener species for which molecular data are available.

In order to evaluate the infestation by anisakids present in elasmobranchs and their distribution in the Argentine Sea, this study was carried at a regional scale with the following aims: 1) to identify those anisakid species present in skates under exploitation; 2) to characterize quantitatively these infestations and 3) to determine those factors driving the variability in parasite burdens across skate species. A total of 351 skates, belonging to 3 species (218 Sympterygia bonapartii, 86 Zearaja chilensis and 47 Atlantoraja castelnaui) and from different localities of the Argentine Sea were examined for anisakids. Parasites were found in the stomach wall at high prevalence in some samples. Based on morphology and mtDNA cox2 sequences analyses (from 24 larval worms), specimens were identified as Anisakis berlandi, A. pegreffii and Pseudoterranova cattani; the last two known as potentially pathogenic for humans. Differential distribution patterns were observed across parasite and hosts species. In general, fish caught in southern and deeper waters exhibited higher loads of Anisakis spp., whereas infestation levels by P. cattani increase in larger skates. Taking into account that the mere presence of worms or their antigens in fish meat can provoke allergic responses, information on distribution of parasites and their variability is essential for the implementation of food safety practices., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Neonchocotyle violantei n. sp. (Monogenea: Hexabothriidae) infects the gill of the Atlantic guitarfish, Pseudobatos lentiginosus (Rhinopristiformes, Rhinobatidae) from littoral waters of Celestún, Yucatán, Mexico. It is assigned to Neonchocotyle because it has, among other features, an asymmetrical haptor, a seminal receptacle, a smooth oötype, and an egg with two elongate filaments. It differs from Neonchocotyle pastinacae, the only congener, by having a small body (821 long by 315 wide, length to width = 2.6:1), two pairs of microhooks between the haptoral appendix suckers, extracaecal (submarginal) vaginal pores, and 5-9 testes. This is the first record of a species of Neonchocotyle in the Gulf of Mexico, the first monogenean reported from P. lentiginosus in Mexico and the second species of Hexabothriidae reported from Mexico.

During a survey on the myxosporean fauna of Rajiformes from the Atlantic coast of Argentina, in waters off Buenos Aires Province (34°-42°S; 53°-62°W), the gall bladders of 217 specimens belonging to seven species of skates, representatives of two families, were examined. As a result, three species of Chloromyxum Mingazzini, 1890, namely C. atlantoraji n. sp., C. zearaji n. sp. and C. riorajum Azevedo, Casal, Garcia, Matos, Teles-Grilo and Matos, 2009 were found infecting three endemic host species, the spotback skate Atlantoraja castelnaui (Arhynchobatidae), the yellownose skate Zearaja chilensis (Rajidae) and the Rio skate Rioraja agassizii (Arhynchobatidae), respectively. These species were described based on myxospore morphology and morphometry characterization, as well as by providing their small subunit ribosomal DNA (SSU rDNA) sequences. The SSU rDNA-based phylogenetic analyses showed that these three species constituted a well-established monophyletic subclade within the marine Chloromyxum clade, while branches subtending the other Chloromyxum species were poorly resolved or unresolved, independently of the host taxonomic identities (Carchariniformes, Myliobatiformes, Orectolobiformes, Pristiophoriformes, Rajiformes, Squaliformes and Torpediniformes) and/or host geographic distribution (Atlantic coast of Portugal, Atlantic coast of the USA, Australian waters or Mediterranean Sea). The possible causes of these discrepancies are discussed, providing new insights into the phylogeny of the marine Chloromyxum clade., (© D.M.P. Cantatore et al., published by EDP Sciences, 2018.)

The helminthological examination of nine individuals of Aetobatus cf. narinari (spotted eagle ray; raya pinta; arraia pintada) revealed the presence of an undescribed species of cestode of the genus Acanthobothrium. The stingrays were collected from four locations in México: Laguna Términos, south of Isla del Carmen and the marine waters north of Isla del Carmen and Champotón, in the State of Campeche, and Isla Holbox, State of Quintana Roo. The new species, nominated Acanthobothrium marquesi, is a category 3 species (i.e, the strobila is long, has more than 50 proglottids, the numerous testicles greater than 80, and has asymmetrically-lobed ovaries); at the present, the only category 3 species that has been reported in the Western Atlantic Ocean is Acanthobothrium tortum. Acanthobothrium marquesi n. sp. can be distinguished from A. tortum by length (26.1 cm vs. 10.6 cm), greater number of proglottids (1,549 vs. 656), a larger scolex (707 µm long by 872 µm wide vs. 699 µm long by 665 µm wide), larger bothridia (626 µm long by 274 µm wide vs. 563 µm long by 238 µm wide). This is the first report of a species of Acanthobothrium from the Mexican coast of the Gulf México.

Blood flukes (Aporocotylidae) of actinopterygians (bony fishes) have been shown to infect freshwater gastropods and marine polychaetes as intermediate hosts. However, no life cycle is known for any aporocotylid of chondrichthyans (cartilaginous fishes) and no adult aporocotylid has been linked to a cercaria infecting a bivalve. Here we report two novel infections that fill these gaps. Cercariae consistent with the family Aporocotylidae were found developing in sporocysts in the gonad of the surf pipi, Donax deltoides Lamarck, 1818 (Bivalvia: Donacidae), from Stockton Beach, central New South Wales, Australia. Adult aporocotylids were found in the heart of the giant shovelnose ray, Glaucostegus typus (Anonymous [Bennett], 1830), from Moreton Bay, southeastern Queensland, Australia. Phylogenetic analyses of the 28S rDNA region generated from the new specimens resulted in phylograms in which the two parasites form a strongly supported clade with Chimaerohemecus trondheimensis van der Land, 1967, the only aporocotylid known from a holocephalan and the only other chondrichthyan-infecting aporocotylid for which sequence data are available. Most marine aporocotylids of actinopterygians also form a strongly supported clade. These findings lead us to hypothesise that the aporocotylids of chondrichthyans are distinct from all other blood flukes in infecting bivalves as intermediate hosts. Putative cophyly between three major blood fluke clades and both definitive and intermediate host groups is consistent with diversification of the Schistosomatoidea over 400million years ago., (Copyright © 2017 Australian Society for Parasitology. All rights reserved.)

Mycteronastes Kearn and Beverley-Burton, 1990 (Monogenoidea: Monocotylidae: Merizocotylinae) was resurrected from subjective synonymy with Merizocotyle Cerfontaine, 1894 , and its diagnosis was emended to include monocotylids with a haptor lacking a central loculus and having 5 peripheral (2 bilateral pairs and an unpaired anteromedial loculus), 1 interhamular, and 17 marginal loculi. The 3 species of Mycteronastes accepted herein are parasitic within the olfactory sacs of rays and sawfishes: Mycteronastes icopae ( Beverley-Burton and Williams, 1989 ) Kearn and Beverley-Burton, 1990 (type species) from the giant shovelnose ray, Glaucostegus typus (Anonymous (Bennett)) (Glaucostegidae), in the southwestern Pacific Ocean; Mycteronastes undulatae Kearn and Beverley-Burton, 1990 from the undulate ray, Raja undulata Lacepède (Rajidae), in the northeastern Atlantic Ocean; and Mycteronastes caalusi n. sp. from the smalltooth sawfish, Pristis pectinata Latham (Pristidae), in the Gulf of Mexico. Mycteronastes caalusi is most easily differentiated from its congeners by the combination of having 2 median cephalic papillae, an oval haptor that is wider than the body proper and lacks a deeply scalloped margin, a comparatively large anteromedial peripheral loculus, an unsclerotized male copulatory organ that is wholly anterior to the vaginal pores, a relatively small distal portion of the uterus (ootype chamber) that is mostly anterior to the vaginae, and a delicate uterus. The present study is the first report of a monocotylid from the olfactory sacs of P. pectinata and the first record of a species of Mycteronastes from the Gulf of Mexico. Notes on the taxonomy and systematics of some species assigned to Calicotyle Diesing, 1850 (Monocotylidae: Calicotylinae) are included.

A new species of Empruthotrema Johnston & Tiegs, 1922 is described based on specimens collected from the olfactory sacs of smooth butterfly rays Gymnura micrura (Bloch & Schneider) captured in Mobile Bay (northcentral Gulf of Mexico), Alabama, USA. Empruthotrema longipenis n. sp. is most similar to the type-species Empruthotrema raiae (MacCallum, 1916) Johnston & Tiegs, 1922 by having 12 marginal and two interhamular loculi with members of haptoral hook pair 1 located midway along the periphery of each interhamular loculus and those of hook pair 2 located at the marginal termini of the bilateral septa flanking the interhamular loculi. Empruthotrema longipenis n. sp. differs from E. raiae by having a much longer male copulatory organ and from its remaining congeners by the sinistral and extracecal ejaculatory bulb flanking the pharynx, the number of interhamular and marginal septa, and the distribution of hook pairs 1 and 2 along the haptoral margin. This is the first report of a monocotylid from the smooth butterfly ray and from Mobile Bay. The diversity of haptoral morphotypes among the currently accepted species of Empruthotrema is detailed and discussed in the context of monophyly of the genus.

Pseudanisakis argentinensis n. sp. is proposed to accommodate parasitic nematodes found in six skate species (Rajidae and Arhynchobatidae) examined from southern Southwest Atlantic waters. The new species differs from its congeners by the following combination of characters: a cupola on each lip, males with 8-12 pairs of precloacal genital papillae, a larger size for both males and females, a greater length-to-breadth ratio of the ventriculus and the presence of a small knob on the tip of the tail. Allometric growth was observed for several morphometric features; however, the slopes of the allometric relationships across host species exhibited non-significant differences and were considered as a strong evidence for conspecificity. Congruent results were obtained after the genetic characterization of the mitochondrial cytochrome c oxidase subunit 1 gene of worms obtained from different skate species, whose values of genetic divergence (1.3) lay within the range of intraspecific variation. Previous records of specimens referred to as Pseudanisakis tricupola in skates from South American waters are regarded as conspecific with P. argentinensis n. sp.

Much progress has recently been made in revising the taxonomic assignments of genera originally classified in the polyphyletic "Tetraphyllidea." Many of these genera, including Echeneibothrium, were accommodated in the order Rhinebothriidea. However, beyond this larger taxonomic action, little work has been conducted on this genus over the past 50 yr. Consequently, the criteria used for characterizing species of Echeneibothrium have lagged behind those typically used in more modern descriptions of elasmobranch-hosted cestode taxa. A series of collecting trips to Chile to obtain cestodes from the yellownose skate, Dipturus chilensis , provided a unique opportunity to apply modern morphological and molecular methods to investigate the 3 species of Echeneibothrium reported parasitizing this skate, specifically Echeneibothrium megalosoma, Echeneibothrium multiloculatum, and Echeneibothrium williamsi. In addition to redescribing all 3 species, using morphological data from light and scanning electron microscopy, maximum likelihood and bayesian inference phylogenetic analyses of the D1-D3 regions of the 28S rDNA gene were conducted to assess their relationships among other echeneibothriids for which comparable data are available. Sequencing of 59 specimens representing these 3 species of Echeneibothrium allowed us to assess the intra- and interspecific variation in the 28S rDNA gene. The redescriptions use standardized terminology for scolex morphology, proglottid anatomy, and microthrix forms and pattern; they also expand on the original descriptions to include data on scolex size, ovary size, vas deferens and vaginal configurations, testes arrangement, and genital pore position. Our morphological work led to a major reinterpretation of the scolex morphology with the recognition that all 3 species bear an apical bothridial sucker, rather than an apical loculus, prompting emendation of the diagnosis for the family Echeneibothriidae. The presence of a band of spinitriches at the apex of the apical modification of the scolex proper seems to represent an important feature for distinguishing the 2 portions of the myzorhynchus across species. Intraspecific variation ranged from 0 to 7 bp across species and interspecific variation ranged from a low of 39-46 bp between E. williamsi and E. multiloculatum to a high of 61-66 bp between E. multiloculatum and E. megalosoma. Phylogenetic analyses indicate that the 3 species of Echeneibothrium hosted by the yellownose skate are not each other's closest relatives, suggesting multiple colonization events of D. chilensis have occurred. Further phylogenetic investigation is also likely to confirm the status of the genus Pseudanthobothrium as a synonym of Echeneibothrium because its species generally group among members of Echeneibothrium.

Three new species of Aberrapex Jensen, 2001 (Cestoda: Lecanicephalidea) have been collected from species of Myliobatis Cuvier along the coast of Argentina. Aberrapex ludmilae sp. n. parasitises M. goodei Garman in the San Matías Gulf. This species is unique in a combination of features including the shape and extent of the uterus, scolex size, testis distribution, and by lacking an external seminal vesicle and postovarian vitelline follicles. Aberrapex sanmartini sp. n. from M. goodei in San Blas Bay and A. vitalemuttiorum sp. n. from M. ridens Ruocco, Lucifora, Díaz de Astarloa, Mabragaña et Delpiani in coastal waters off Buenos Aires Province, are distinguished from all other congeners by the microthrix pattern on the scolex surface, uterus shape and extension, position of the connection of the uterine duct to the uterus, presence and extension of an external seminal vesicle, and its overall size and number of proglottids. The specimens of M. goodei and M. ridens show locally distinct cestode faunas, which are correlated with well-defined biogeographic regions. Some of these areas correspond with mating and nursery zones for species of Myliobatis.

Three genera of rhinebothriideans, previously referred to as New genus 1, New genus 2 and New genus 4, are erected in the the Anthocephaliidae. New genus 1 is established as Divaricobothrium gen. n., with Divaricobothrium tribelum sp. n. as its type species; Echeneibothrium trifidum Shipley et Hornell, 1906 is transferred to the genus as Divaricobothrium trifidum (Shipley et Hornell, 1906) comb. n. This genus is unique among rhinebothriidean genera in bearing bothridia that are posteriorly deeply divided into two lobes with facial loculi but no apical sucker, and a vagina that extends to near the anterior margin of the proglottid. Its species parasitise Indo-Pacific members of the genera Brevitrygon Last, Naylor et Manjaji-Matsumoto, Maculabatis Last, Naylor et Manjaji-Matsumoto and Pateobatis Last, Naylor et Manjaji-Matsumoto. New genus 2 is established as Barbeaucestus gen. n., with Barbeaucestus jockuschae sp. n. as its type species; Barbeaucestus ralickiae sp. n. is also described. Anthobothrium sexorchidum Williams, 1964 and Rhinebothrium shipleyi Southwell, 1912 are transferred to the genus as Barbeaucestus sexorchidus (Williams, 1964) comb. n. and Barbeaucestus shipleyi (Southwell, 1912) comb. n., respectively. This genus is unique among rhinebothriidean genera in that its bothridia are substantially wider than long, bear an apical sucker and at least one row of two or more facial loculi in their anterior half. Its species parasitise the genera Neotrygon Castelnau and Taeniura Müller et Henle. New genus 4 is established as Sungaicestus gen. n. with transfer of Rhinebothrium kinabatanganensis Healy, 2006, as Sungaicestus kinabatanganensis (Healy, 2006) comb. n., as its type species. Among the genera of its order, this genus most closely resembles Rhinebothrium Linton, 1890, however, despite the original description, the bothridia were found to bear, rather than lack, apical suckers. This monotypic genus is known only from the freshwater stingray Urogymnus polylepis (Müller et Henle). The familial diagnosis of the Anthocephaliidae Ruhnke, Caira et Cox, 2015 is emended. The family now houses five genera.

Spermatological characters of Dictyocotyle coeliaca Nybelin, a unique endoparasitic monogenean from the body cavity of the ray Amblyraja radiata (Elasmobranchii: Rajidae), was investigated by means of scanning and transmission electron microscopy for the first time. The process of the spermatozoon formation begins with the appearance of the differentiation zone which contains two centrioles. Subsequently developed two free flagella rotate to lie parallel before their fusing. After fusion, both the mitochondrion and nucleus migrate alongside the axonemes. Spermatids are formed within parallel cytoplasmic canals. During late spermiogenesis, an electron-dense spiral end-piece is formed proximally to the centriolar region of some spermatids. At the end of spermiogenesis, this end-piece is separated by a plasma membrane from the late spermatid and remains in the residual cytoplasm when spermatozoa are released into the testis lumen. The mature spermatozoon of D. coeliaca contains two parallel axonemes with the 9 + "1" trepaxonematan pattern, mitochondrion, nucleus, parallel cortical microtubules, and electron-dense granules. Especially the presence of electron-dense granules, occurring frequenly in the spermatozoa of endoparasitic flatworms, may indicate an adaptation to endoparasitic lifestyle in D. coeliaca. The anterior extremity of the male gamete contains one centriolar derivative, a small component of the second centriolar derivative and anterior extremity of the mitochondrion. The posterior extremity of the mature spematozoon exhibits tubular elements of the disorganized axoneme. Variations of the spermatozoon ultrastructural characters within monocotylid monogeneans and possible evolutionary significance of glycogen in sperm to the endoparasitic habit are discussed.

A new lecanicephalidean genus is erected for cestodes previously recognised as "New Genus 12" (Polypocephalidae) in a phylogenetic analysis of the interrelationship of members of this order. Examination of the cestode fauna of the mangrove whipray, Urogymnus granulatus (Macleay) (Myliobatiformes: Dasyatidae) from the Solomon Islands and northern Australia revealed the existence of specimens representing two new species, consistent in morphology with "New Genus 12." Corollapex gen. n. is unique among the 24 valid lecanicephalidean genera in its possession of an apical organ in the form of an external retractable central disk surrounded by eight concave muscular, membrane-bound pads and an internal heterogeneous glandular component. The two new species described herein, Corollapex cairae sp. n. (type species) and Corollapex tingoi sp. n., differ from one another in overall size and number of mature and immature proglottids, and are noted to demonstrate a differential distribution between mature and juvenile host individuals. Additional species diversity in the new genus, beyond C. cairae sp. n., C. tingoi sp. n., and "New Genus 12 n. sp. 1" of Jensen et al. (2016) is suggested. Corollapex gen. n. appears to be restricted to dasyatid hosts in the Indo-West Pacific region.

This study provides a parasitological analysis of the elasmobranch species caught in the northern and central Adriatic Sea. Sixty-two marine leeches were recorded on 747 individuals of Raja clavata Linnaeus, 1758 (thornback ray), Myliobatis aquila Linnaeus, 1758 (common eagle ray), and Torpedo marmorata Risso, 1810 (marbled torpedo ray) caught in 56 hauls over a 5 yr period. All leeches were identified as Pontobdella muricata, which is a typical ectoparasite of benthic elasmobranchs. The prevalence of infection ranged from 7.11% on R. clavata to 12.00% on M. aquila. The intensity of infection, the preferential sites of attachment to the host, and the periodicity of infection were evaluated.

A new species of the cyclopoid copepod genus Ergasilus von Nordmann, 1832 is described based on material collected from the gills of an elasmobranch, Himantura oxyrhyncha (Sauvage, 1878), collected in the Java Sea off the coast of West Kalimantan, Indonesia. To justify the establishment of the new species, Ergasilus kimi sp. nov., detailed comparisons are made with the 28 congeneric species that share the combination of a 3-segmented leg 1 endopod and the presence of 2 setae on the free exopodal segment of leg 5. This is the fourth report of an Ergasilus species infecting an elasmobranch and it is concluded that each represents an independent colonization event of elasmobranchs as hosts.

The olfactory sacs of 488 specimens belonging to 18 species of rajid and arhynchobatid skates from the Argentine Sea were sampled for parasites. No parasitic copepods were found in 11 host species, but siphonostomatoid specimens referable to Kroeyerina Wilson, 1932 (Kroyeriidae) and Brianella corniger Wilson, 1915 (Lernaeopodidae) were found on the spotback skate Atlantoraja castelnaui (Miranda Ribeiro, 1907), the smallnose fanskate Sympterygia bonapartii Müller & Henle, 1841, the bignose fanskate Sympterygia acuta Garman, 1877 and the zipper sand skate Psammobatis extenta (Garman, 1913) (Rajiformes: Arhynchobatidae). Additionally, specimens of B. corniger were found in the olfactory sacs of the Rio skate Rioraja agassizii (Müller & Henle, 1841) and attached to the pectoral fins of the Magellan skate Bathyraja magellanica (Philippi, 1902) and the smallthorn sand skate Psammobatis rudis Günther, 1870. A new species, Kroeyerina sudamericana sp. nov., is described and illustrated. The new species most closely resembles Kroeyerina nasuta Wilson, 1932, but can be distinguished from it by the different armature of the antennule, a proportionally shorter genital complex and the chela of the antenna which, when closed, leaves a gap between the corpus and claw, the latter having no spines. The new species represents the first record of Kroeyerina in South American marine waters. The present study also extends the distribution range of B. corniger, previously known only from the Pacific, to include Atlantic waters, and records seven new host species, all of which are members of the Arhynchobatidae.

The genus Schistobrachia Kabata, 1964 (Lernaeopodidae: Siphonostomatoida) currently accommodates five species of which two infect holocephalans and three utilize elasmobranchs. Kensley & Grindley (1973) reported three females from "Dipturus batis" (Linnaeus, 1758) collected in Table Bay, South Africa, which they assigned to S. ramosa (Krøyer, 1863), a species previously known only from the North Atlantic. Re-examination of these specimens (labelled Charopinus ramosus Krøyer, 1863 and deposited in the Iziko South African Museum) and additional Schistobrachia material newly collected from the gills of various Rajiformes off the South African west and south coasts, showed that Kensley & Grindley's (1973) earlier record of S. ramosa was misidentified and in reality represents a distinct species, S. kabata sp. nov. Both sexes of the new species are described using light and/or scanning electron microscopy.