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A new genus, Cordicestus, is proposed to accommodate proteocephalid tapeworms parasitising gars (Lepisosteiformes: Lepisosteidae) in North and Central America that were previously placed in the polyphyletic genus Proteocephalus Weinland, 1858. The new genus differs from other proteocephalid genera by the particular morphology of the scolex, which is small, protrudes apically but has no apical organ, and bears flat, heart-shaped (= cordis) suckers. In addition, the species of the new genus have an elongated cirrus sac with an almost straight internal vas deferens and wide, sinuous ventral osmoregulatory canals with secondary canals directed outwards. The type species of the new genus, Cordicestus singularis (La Rue, 1911) n. comb., is redescribed based on new material from the shortnose gar, Lepisosteus platostomus Rafinesque (type host), and the spotted gar, L. oculatus Winchell, in the United States. Cordicestus rafaeli n. sp. is described from the tropical gar, Atractosteus tropicus Gill, in Mexico. The new species differs from its relatives primarily by the presence of craspedote proglottids (acraspedote in other species) and some biometric features. All species of Cordicestus are revised, including unidentified specimens from A. tropicus and the Cuban gar A. tristoechus (Bloch and Schneider) in Nicaragua and Cuba, respectively, which may be new species, and a key to the identification of these taxa is provided. Molecular data available for two nominal species of the new genus indicate the possible existence of another species of Cordicestus in Lepisosteus in the USA., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Based on previous molecular phylogenetic analyses, Bothriocestus n. gen. is erected to accommodate bothriocephalid tapeworms that have an elongate scolex, a well-developed apical disc, and a narrow neck region, parasitize freshwater fishes in the Holarctic, and were previously placed in the polyphyletic genus Bothriocephalus Rudolphi, 1808 (Cestoda: Bothriocephalidea). Bothriocestus claviceps (Goeze, 1782) n. comb., a parasite of eels (Anguilla spp.) in the Holarctic region, is designated as the type species. Another species of the new genus, Bothriocestus cuspidatus (Cooper, 1917) (syn. Bothriocephalus cuspidatusCooper, 1917) is redescribed from type and voucher specimens, and new material from the type host, the walleye, Sander vitreus (Mitchill, 1818) (Perciformes: Percidae), in Manitoba and Ontario (where the type locality is located) (Canada) and in New York state and Wisconsin. Bothriocestus cuspidatus of S. vitreus is characterized primarily by the possession of a narrow, long strobila (total length up to 18 cm) composed of distinctly craspedote, trapezoidal proglottids, with primary, secondary, and tertiary proglottids differing in size, and by an arrow-shaped (=cuspidatus) scolex that is distinctly broader than the first proglottids, widest near the base in lateral view and gradually becoming broader toward the anterior end in dorsoventral view. A "dwarf" form of B. cuspidatus (total length of 9-27 mm) from Johnny darter, Etheostoma nigrum Rafinesque, 1820, and tessellated darter, Etheostoma olmstedi Storer, 1842 (both Percidae: Etheostominae), is also characterized morphologically in the present paper., (© American Society of Parasitologists 2023.)

Proteocephalid tapeworms of frogs of the family Ranidae ('true' frogs) are reviewed with emphasis on their species diversity, host specificity and geographical distribution. New molecular data (nuclear lsrDNA and mitochondrial COI sequences) are presented for tapeworms of four species of ranid frogs in North America, including the poorly known Ophiotaenia saphena Osler, 1931 of Rana clamitans Latreille and R. catesbeiana (Shaw), which is redescribed using new material from Arkansas, USA. Tapeworms of R. sphenocephala (Cope) and R. pipiens Schreber, the latter previously identified as O. saphena, represent another, putative new species, but are not formally described due to insufficient available material. Proteocephalus papuensis Bursey, Goldberg et Kraus, 2008 from Sylvirana supragrisea (Menzies) is transferred to Ophiotaenia La Rue, 1911 as a new combination. After a critical review of the literature, only nine nominal species of Ophiotaenia are recognised as valid, which is in contrast to the large number of ranid frogs (> 440 spp.). The reasons for this striking disparity are briefly discussed, and a key based on morphology is presented for the identification of all species of Ophiotaenia from the Ranidae. Molecular data are available for only two taxa from North America that form a monophyletic group. The relationships among tapeworms of ranid frogs occurring in other zoogeographical regions are not yet known. The taxonomic status of Batrachotaenia Rudin, 1917, which was erected to accommodate proteocephalids from amphibians, is also discussed. To facilitate future studies, a tabulated summary of all 32 species of proteocephalids belonging to three genera reported from amphibians (frogs and salamanders) is presented, with information on their hosts, distribution, and taxonomically important characters, including key measurements.

The tapeworms of fishes (Chondrichthyes and Actinopterygii) account one-third (1670 from around 5000) of the total tapeworm (Platyhelminthes: Cestoda) species diversity. In total 1186 species from 9 orders occur as adults in elasmobranchs (sharks, rays and chimaeras), and 484 species from 8 orders mature in ray-finned fishes (referred to here as teleosts). Teleost tapeworms are dominated by freshwater species (78%), but only 3% of elasmobranch tapeworms are known from freshwater rays of South America and Asia (Borneo). In the last 2 decades, vast progress has been made in understanding species diversity, host associations and interrelationships among fish tapeworms. In total, 172 new species have been described since 2017 (149 from elasmobranchs and 23 from teleosts; invalidly described taxa are not included, especially those from the Oriental region). Molecular data, however, largely limited to a few molecular markers (mainly 28S rDNA, but also 18S and cox 1), are available for about 40% of fish tapeworm species. They allowed us to significantly improve our understanding of their interrelationships, including proposals of a new, more natural classification at the higher-taxonomy level (orders and families) as well as at the lower-taxonomy level (genera). In this review, we summarize the main advances and provide perspectives for future research.

Based on morphological and molecular data, a new species of tapeworm, Bothriocephalus kupermani n. sp., is described from pumpkinseed, Lepomis gibbosus (Linnaeus, 1758) (type host), and green sunfish, L. cyanellus Rafinesque, 1819 (Actinopterygii: Centrarchidae) in the United States. The new species differs from its North American congeners mainly in the shape of its scolex, which is almost rectangular in dorsoventral and lateral views (nearly parallel margins in the bothrial region), with shallow, wide bothria, and by an extensive field of vitelline follicles that are also variably present, albeit more sparsely, medially in the cortex of the ovarian and uterine areas. This tapeworm appears to be typically associated with Lepomis sunfishes. Examination of museum specimens of Bothriocephalus species from Lepomis spp. indicates that the tapeworm also parasitizes bluegill, Lepomis macrochirus, longear sunfish, Lepomis megalotis, and that previous records of Bothriocephalus cuspidatus and Bothriocephalus claviceps in these fishes are of the new species, B. kupermani., (© American Society of Parasitologists 2022.)

A new genus, Mystocestus, is proposed to accommodate a new species, Mystocestus anindoi n. g., n. sp. from Mystus vittatus (Bloch) (type host) in West Bengal and Mystus cavasius (Hamilton) (Siluriformes: Bagridae) in Maharashtra, India. The new genus is most similar to Lucknowia Gupta, 1961 in the shape of the body, which is elongate, slightly tapering towards the anterior end, and scolex, which is digitiform, but differs in the shape of the ovary, which is H-shaped (vs. inverted A-shaped in Lucknowia), the absence of a seminal receptacle (present in Lucknowia) and exclusively cortical vitelline follicles (vs. some follicles in the medulla in the latter genus). Molecular data support the erection of the new genus and place it close to Bovienia Fuhrmann, 1931, species of which can be easily distinguished by exclusively lateral vitelline follicles (lateral and median in the new genus), the presence of a seminal receptacle (absent in Mystocestus) and scolex shape (digitiform, with blunt or slightly concave anterior edge in the new genus vs. small, unspecialized or spatulate in Bovienia). The convoluted taxonomy of tapeworms placed in Mystoides Mathur, 1992 is critically reviewed to clean up taxonomic chaos in Indo-Malayan caryophyllideans. Mystoides was erected in an unpublished PhD thesis and thus its generic name becomes unavailable and also, its type species is conspecific with Lucknowia fossilisi Gupta, 1961 from the stinging catfish, Heteropneustes fossilis (Bloch). Other species of this genus are also conspecific with L. fossilisi. In addition, specific names of most of these taxa are unavailable because they were described in unpublished theses or conference abstracts. Based on recent revisions of Indo-Malayan caryophyllideans, the following nine genera with 15 species are considered valid (numbers of species of individual genera are provided in parentheses): Bovienia (3), Djombangia (1), Lucknowia (2), Lytocestus (2), Mystocestus (1), Pseudocaryophyllaeus (2) (all family Lytocestidae); Adenoscolex (1), Lobulovarium (2), Paracaryophyllaeus (1) (all family Caryophyllaeidae).

The proteocephalid genus Pseudoendorchis (Cestoda: Onchoproteocephalidea) has recently been proposed to accommodate seven species/species-level lineages of tapeworm parasites of catfishes (Siluriformes) in the Neotropical region, based on integration of genetic information, and morphological and ecological data. Its members are typified by having a large Mehlis' gland, representing more than 1/5 (usually 1/4-1/2) of proglottid width, and the vagina always anterior to the cirrus-sac. Critical examination of previously unstudied museum cestodes tentatively designated as Pseudoendorchis sp. 3 from Megalonema platycephalum (Pimelodidae) in the Peruvian Amazon made it possible to formally describe this taxon and to differentiate it from all congeneric species. The new species, which is the first parasite of M. platycephalum ever recorded, is characterised mainly by having the scolex bearing four uniloculate suckers (biloculate in all nominal species of the genus), the lowest relative surface of the ovary (ratio of its surface to that of the whole proglottid) among species of the genus (< 9% versus > 11%, usually 15-20%), and an extraordinarily large Mehlis' gland (its diameter represents 41-50% of proglottid width). Morphology of the terminal portion of the vaginal canals in proteocephalids is briefly discussed., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Tapeworms (Cestoda) represents a species rich (about 5000 species) group of flatworms (Neodermata) parasitizing all groups of vertebrates including humans, with about 1000 species parasitizing elasmobranchs and almost 500 occurring in teleosts as adults. They are common parasites of cultured fish, both as adults and larvae (metacestodes), but only few adult tapeworms are actually pathogenic for their fish hosts. In contrast, cestode larvae can be harmful for fish, especially plerocercoids migrating throughout their tissue and internal organs. Current knowledge of host-parasite relationships, including immune response of fish infected with tapeworms, is still insufficient to enable adequate control of cestodoses, and most data available were obtained several decades ago. Treatment of fish infected with adult tapeworms is effective, especially with praziquantel, whereas the treatment of metacestodes is problematic. Control measures include interruption of the complex life cycle and prevention of transport of uninspected fish to new region., (© 2021 John Wiley & Sons Ltd.)

Tapeworms of the genus Paracaryophyllaeus Kulakovskaya, 1961 (Cestoda: Caryophyllidea) are specific parasites of loaches (Cypriniformes: Cobitoidea) and occur almost exclusively in the Palaearctic region. The only exception and example of vicariance over the borders of two zoogeographical regions is Paracaryophyllaeus lepidocephali (Kundu, 1985), an insufficiently known species described from the Indomalayan region, with uncertain generic allocation. In the present paper, the species is redescribed based on new material collected from the type host, Lepidocephalichthys guntea, in West Bengal, India. Molecular data reveal this species as a member of Paracaryophyllaeus, within which it is the most closely related to P. cf. gotoi from Misgurnus anguillicaudatus in China and Japan on the basis of large subunit of ribosomal nuclear DNA (28S rDNA). Generic position of P. lepidocephali examined herein is also confirmed by morphology including cross sections, in particular, by a small, cylindrical body, medullary testes with testicular fields crossing the anterior margin of the cirrus sac, medullary vitelline follicles, with some follicles paramuscular, a shallow common genital atrium, short vagina and uterus not extending anteriorly beyond the cirrus sac. It differs from all Palaearctic congeners but Paracaryophyllaeus vladkae Scholz, Oros and Aydogdu, 2014 by the testicular field crossing the anterior margin of the cirrus sac. It differs from P. vladkae by more anterior position of the first vitelline follicles compared to the first testes. This species is a unique example of a fish tapeworm crossing the borders of the Palaearctic and Indomalayan zoogeographical regions., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A new genus, Megancestus n. gen., is proposed to accommodate the caryophyllidean tapeworm Biacetabulum carpiodi Mackiewicz, 1969 from carpsuckers and quillback (Carpiodes spp.) in North America. This species is not closely related to other species of Biacetabulum Hunter, 1927 and is transferred to a newly erected genus. This new genus is typified by the possession of a small body (total length of 3.1-7.5 mm) with a scolex that bears a pair of large acetabulum-like loculi, two pairs of shallow lateral loculi, and a slightly convex apical disc, testes arranged in one or two layers, oval, thick-walled cirrus-sac, well-developed external seminal vesicle, separate gonopores, H-shaped ovary, few median vitelline follicles, and the uterus extending by a single loop anterior to the cirrus-sac. Megancestus differs from all Nearctic caryophyllidean genera (family Capingentidae), including Biacetabulum, by vitelline follicles dorsal to the ovary that connect the preovarian and postovarian vitelline fields. The most closely related Hunterella Mackiewicz et McCrae, 1962 differs by shape of the scolex (tholate, i.e., devoid of any loculi), dumbbell-shaped ovary and the uterus not extending anterior to the cirrus-sac. Megancestus carpiodi (Mackiewicz, 1969) n. comb. is the only species of the genus and it is a stenoxenous parasite, which has been found only in the river carpsucker (Carpiodes carpio-type host), quillback (Carpiodes cyprinus) and highfin carpsucker (Carpiodes velifer) (Catostomidae: Ictiobinae) in the lower and middle Mississippi basin.

Species diversity and interrelationships of tapeworms of the genus Kapsulotaenia Freze, 1963 (Proteocephalidae: Acanthotaeniinae), parasites of lizards, especially monitors (Varanus spp.) in the Australasian region, were re-assessed using an interdisciplinary approach. Molecular phylogenetic analyses of newly characterized lsrDNA and cox1 sequences confirmed monophyly of the genus, which is typified by the presence of eggs in capsules, and also indicated a strict (oioxenous) level of host specificity of its species thus revealing unexpected species diversity. Diagnoses of insufficiently described species were amended based on a study of the types and freshly collected specimens and, in addition, three new species were described. A list of ten species of the genus recognized as valid is provided, including illustrations of taxonomically important structures of poorly known taxa. Kapsulotaenia beveridgei n. sp. from V. rosenbergi in Australia differs from all other species of Kapsulotaenia but K. frezei and K. saccifera by having a lower number of testes and an absence of banana-shaped clusters of eggs. Kapsulotaenia cannoni n. sp. from V. gouldii can be distinguished from all species but K. chisholmae by a smaller scolex diameter and from all remaining species by its bigger cirrus-sac ratio and a bigger Mehlis' gland/proglottid width ratio. Kapsulotaenia cannoni n. sp. differs from K. chisholmae, by the presence of an armed cirrus and a lower number of eggs in cluster (3-7 versus 8-13). Kapsulotaenia nybelini n. sp., which also occurs in V. gouldii, differs from K. tidswelli, K. frezei and K. beveridgei by having a greater number of testes, and it differs from K. varia by having a smaller relative size of the ovary. It differs from K. saccifera by the absence of banana-shaped cluster, and from K. pythonis by the number of eggs in clusters. Identification keys for all species of Kapsulotaenia and genera of the Acanthotaeniinae are also provided, together with SEM micrographs of three species, including two newly described species.

Morphological and molecular evaluation of tapeworms of the genus Bothriocephalus Rudolphi, 1808 (Cestoda: Bothriocephalidea), based on newly collected and uniformly fixed worms from freshwater fishes in Canada and the United States has revealed unexpected diversity. With a combination of selected morphological features and 4 molecular markers (18S rDNA V8 region, ITS1, ITS2, and COI gene sequences), the following morphotypes and lineages of the Bothriocephalus cuspidatus Cooper, 1917 complex were identified, several of which are specific to their respective fish definitive hosts and may represent separate species: B. cuspidatus sensu stricto from walleye, Sander vitreus (type host), which likely includes a miniature morphotype from Johnny darter, Etheostoma nigrum (both Percidae); Bothriocephalus morphotype from pumpkinseed, Lepomis gibbosus (Centrarchidae); and Bothriocephalus morphotype from rock bass, Ambloplites rupestris (Centrarchidae). The Bothriocephalus morphotype from goldeye, Hiodon alosoides (Hiodontidae), may also represent a separate lineage (possibly Bothriocephalus texomensisSelf, 1954) but requires additional studies. A morphotype from smallmouth bass, Micropterus dolomieu, based on a single specimen, is morphologically and genetically very similar to the morphotype from rock bass. Morphological study of the scolex and strobila of heat-killed and fixed specimens has revealed consistent differences, often subtle, that allowed us to differentiate between these morphotypes., (© American Society of Parasitologists 2020.)

A survey of the species of the Proteocephalus-aggregate from sticklebacks (Actinopterygii: Gasterosteidae) is provided. The occurrence of three species in North America is confirmed: (i) Proteocephalus filicollis (Rudolphi, 1802), which has been reported from the three-spined stickleback, Gasterosteus aculeatus Linnaeus, in the northeastern part of North America (Newfoundland); (ii) Proteocephalus pugetensis Hoff et Hoff, 1929 occurs also in G. aculeatus, but in northwestern North America (British Columbia and Washington); and (iii) Proteocephalus culaeae sp. n., which is described from the brook stickleback, Culaea inconstans (Kirtland), in Manitoba (Canada). Another species, Proteocephalus ambiguus (Dujardin, 1845), a specific parasite of the nine-spined stickleback, Pungitius pungitius (Linnaeus), and type species of the genus, has also been found in North America (Alberta, Canada), but its vouchers are in poor condition and cannot be reliable assigned to this species. Both species reported from three-spined stickleback differ from each other by the shape of the scolex (rounded in P. filicollis versus continuously tapered towards the anterior extremity in P. pugetensis) and the apical sucker (widely oval to subspherical in frontal view in P. filicollis versus flattened in P. pugetensis). Proteocephalus culaeae sp. n. is characterised by a short body composed of a few, continuously widened proglottids, a short scolex narrower than the strobila and devoid of an apical sucker, a short, pyriform cirrus sac, no vaginal sphincter, and few testes. A key to species of the Proteocephalus-aggregate from sticklebacks is provided.

Ictalurid catfishes (Siluriformes) in North America harbor proteocephalid tapeworms of the subfamily Corallobothriinae. Type species of 2 of 3 genera of these tapeworms from ictalurids are redescribed, based on museum and newly collected material. Essexiella fimbriata (Essex, 1928) is typified mainly by a wide, umbrella-shaped scolex with a metascolex formed by numerous folds of tissue, anteriorly directed suckers without sphincters, vitellarium bent inwards posteriorly, "flower-shaped" uterus (with anterior, lateral, and posterior diverticula), and a conspicuously pre-equatorial genital atrium. Verified host records of this cestode are only from 3 species of Ictalurus Rafinesque, 1820. Megathylacoides giganteum (Essex, 1928), which seems to be specific to the channel catfish (Ictalurus punctatus), possesses a globular scolex, with a weakly developed metascolex formed by tissue folds posterior to the suckers, anterolaterally directed suckers with large semilunar sphincters, proglottids that are widest at the level of the genital atrium at the anterior third of the proglottid, and uterine diverticula that do not reach the vitelline follicles laterally. A new subfamily, Essexiellinae Scholz and Barčák, is proposed to accommodate species of EssexiellaScholz, de Chambrier, Mariaux and Kuchta, 2011 (type genus), MegathylacoidesJones, Kerley and Sneed, 1956, and CorallotaeniaFreze, 1965 from ictalurid catfishes in the Nearctic Region. These tapeworms possess a metascolex, medullary genital organs, uterus lined with numerous chromophilic cells, pre-equatorial genital atrium, and uterine development of type 2. The new subfamily was monophyletic in all molecular phylogenetic analyses, being most closely related to 3 Neotropical proteocephalids from the redtail catfish, Phractocephalus hemioliopterus (Bloch and Schneider, 1801), but distant from all remaining proteocephalid tapeworms from freshwater fishes in North America., (© American Society of Parasitologists 2020.)

Tapeworms (Cestoda) of the order Cyclophyllidea include over 3,000 species of intestinal parasites of tetrapods, especially birds and mammals including humans. However, adults of cyclophyllideans have never been found in bony fishes, even though hundreds of thousands of these hosts have been examined for parasites globally over more than 250 years. In the present paper, we report on a unique example of host switching of a tapeworm from birds to teleost fish in Africa. A new genus, Ichthyolepis (Cyclophyllidea: Dilepididae), is erected to accommodate Ichthyolepis africana n. sp., which is the first cyclophyllidean tapeworm that sexually matures in teleost fishes. The new species parasitises several freshwater elephantfishes (Mormyriformes: Mormyridae) including Marcusenius macrolepidotus (type host) in South Africa, Marcusenius senegalensis in Senegal, Mormyrus caschive, M. niloticus and Pollimyrus isodori in the Sudan, and Mormyrus kannume in Egypt. Ichthyolepis n. gen. is typified by a large musculo-glandular apical apparatus with rostellar pouch and a rostellum armed with robust hooks similar in size, but different in shape, deep, sandglass-shaped genital atrium, vaginal atrium and cirrus armed with tiny spines, thick-walled, subspherical cirrus sac, large, lobulated ovary occupying a large part of the median pre-equatorial field of mature proglottids, numerous testes filling almost entirely the postequatorial median field of proglottids, long and narrow, sleeve-like lateral uterine diverticula, and spindle-shaped eggs. Molecular phylogenetics considers Ichthyolepis as a member of the lineage consisting of dilepidids from swifts (Apodidae) in Africa. All fish hosts of the new tapeworm are bottom feeders, live in muddy biotopes and are insectivorous, which indicates that its intermediate hosts may be insect larvae., (Copyright © 2020 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.)

In the present paper, species of the Proteocephalus -aggregate de Chambrier, Zehnder, Vaucher, and Mariaux, 2004 (Cestoda: Proteocephalidae) reported from centrarchid and percid fishes in North America are reviewed, and their taxonomic status is critically assessed based on a study of type specimens and new material from Canada and the United States. The following 3 species, supposedly strictly specific to their fish definitive hosts, are recognized as valid: (1) Proteocephalus fluviatilis Bangham, 1925 (new synonyms Proteocephalus osburni Bangham, 1925 and Proteocephalus microcephalus Haderlie, 1953 ; Proteocephalus ' robustus ' nomen nudum) from the smallmouth and largemouth bass, Micropterus dolomieu (Lacépède) (type host) and Micropterus salmoides (Lacépède) (both Centrarchidae); (2) Proteocephalus luciopercae Wardle, 1932 (new synonym Proteocephalus stizostethi Hunter and Bangham, 1933 ) from the walleye, Sander vitreus (Mitchill) (type host), and sauger, Sander canadensis (Griffith et Smith) (Percidae); and (3) Proteocephalus pearsei La Rue, 1919 , a parasite of the yellow perch, Perca flavescens Mitchill (Percidae). All species are illustrated based on new, properly heat-fixed material. Scanning electron micrographs of the scoleces of percid tapeworms P. luciopercae and P. pearsei , as well as the bass tapeworms P. fluviatilis and Proteocephalus ambloplitis ( Leidy, 1887 ), the latter of which does not belong to this Proteocephalus -aggregate, are provided for the first time together with a simple key to species identification of proteocephalids from centrarchiform and perciform teleost fishes.

A morphological and molecular phylogenetic study of proteocephalid tapeworms of the genus Acanthotaenia von Linstow, 1903, parasites of monitors (Varanidae), was carried out. The type species, A. shipleyi von Linstow, 1903, which was originally described based on an immature specimen from Sri Lanka, is redescribed based on new material from the type host, Varanus salvator, in Sri Lanka, Malaysia, and Vietnam, and its neotype is designated. In addition, Acanthotaenia susanae n. sp. is described from Varanus nebulosus in Vietnam. The new species differs from congeners by the large size of the scolex, width of the rostellum and the number of testes. New molecular data (sequences of lsrDNA and cox1) revealed Acanthotaenia paraphyletic with the inclusion of Australotaenia bunthangi de Chambrier & Scholz, 2012, a parasite of Enhydris enhydris (Ophidia: Homalopsidae) in Cambodia. Molecular data confirm a wide distribution of A. shipleyi (isolates from Malaysia and Vietnam were almost identical) and indicate a strict host specificity (oioxeny) of individual species of the genus. Type specimens of four species made it possible to supplement their morphological descriptions. A survey of all species of Acanthotaenia recognised as valid is presented and the following taxonomic changes are proposed: Acanthotaenia pythonis Wahid, 1968 described from the green python, Morelia viridis, in a zoo, is transferred to Kapsulotaenia as Kapsulotaenia pythonis (Wahid, 1968) n. comb., because it possesses intrauterine eggs grouped in capsules. Acanthotaenia gracilis (Beddard, 1913) from Varanus varius in Australia is considered to be species inquirenda because its original descriptions did not contain sufficient data for adequate circumscription and differentiation from congeners and type material was not available. Generic diagnosis of Acanthotaenia is amended and a key to its seven species is provided.

A new species of the recently erected genus of proteocephalid cestodes, Synbranchiella Arredondo, Alves and Gil de Pertierra, 2017 , is described based on specimens found in the mountain mullet, Dajaus monticola (Bancroft, 1834), from Costa Rica. The new species is placed in Synbranchiella because of the cortical position of the genital organs (typical of the former subfamily Monticelliinae); a robust scolex (lacking a metascolex) having a dome-shaped apex and biloculate suckers (lacking free posterior margins); vitelline follicles in 2 narrow lateral bands; a vagina always anterior to the cirrus-sac; and a genital pore that is markedly pre-equatorial, i.e., close to the anterior margin of proglottids. The new species, Synbranchiella megacirrus, differs from the type and only other species of the genus, Synbranchiella mabelae Arredondo, Alves and Gil de Pertierra, 2017 , that infects the marbled swamp eel, Synbranchus marmoratus Bloch, 1795, in Argentina by the absence of preporal vitelline follicles (present in S. mabelae); a well-developed, large, elongate vaginal sphincter (small and ring-like in S. mabelae); and a large cirrus-sac relative to the proglottid size (cirrus-sac length is on average 48% of the proglottid width in S. megacirrus vs. 31% in the latter species). This is the first adult tapeworm reported from mountain mullet and the first record of the genus outside of South America, thereby greatly extending the range of distribution of species of Synbranchiella.

The tapeworm Sciadocephalus megalodiscus Diesing, 1850 (Cestoda: Proteocephalidae), is redescribed based on newly collected specimens parasitizing tucunare peacock bass, Cichla monoculus Agassiz, 1831 (Perciformes: Cichlidae), in the Peruvian Amazon. Even though this cestode was redescribed 2 decades ago, that redescription did not report some of the unique features of this species. The most unusual characteristics of the species are (1) peculiar formation of the uterus, with fast formation of numerous, tightly packed diverticula protruding ventrally and dorsally, with simultaneous disintegration of the ovary and vitelline follicles in the first pregravid proglottids; (2) inverted umbrella-shaped scolex with a well-developed apical sucker; (3) a large-sized, follicular (grape cluster-like) ovary, which occupies most of the central (median) third of proglottids, with the ovarian isthmus situated almost equatorially; (4) regular alternation of genital pores; (5) a well-developed internal seminal vesicle; and (6) a small-sized strobila (shorter than 6 mm) consisting of few proglottids (15-20). Preliminary molecular data reveal S. megalodiscus to be most closely related to Cichlidocestus gillesi, the type species of the recently erected Cichlidocestus de Chambrier, Pinacho-Pinacho, Hernández-Orts, and Scholz, 2017. Species of both genera parasitize Neotropical cichlids and are unique among all proteocephalids in the shape and position of the ovary. They also share other morphological characteristics unusual among other proteocephalids, and thus these 2 genera can be considered good candidates to be placed in a new, higher-level taxon such as separate subfamily or even family when a new, more natural classification of the Proteocephalidae is proposed.

We describe the development of ready-to-use set of fifteen polymorphic microsatellite markers to benefit future population biology and phylogeographic studies on the invasive Asian fish tapeworm Schyzocotyle acheilognathi. The microsatellite loci were selected from partial Illumina shotgun genome sequences of three parasite specimens and their universality tested on a set of 12 geographically distant populations of the parasite. Particularly low levels of heterozygosity have been detected in the Chinese population pointing towards possible hidden population structure that deserves further attention in future population genetic studies., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The Asian fish tapeworm (AFT), Schyzocotyle acheilognathi, is a notorious and highly successful invasive parasite reported in a wide spectrum of freshwater fishes, and new reports of its spread continue to emerge. To date, no thorough review of its worldwide distribution and host associations is available. In the present work, we collected information from 651 articles up until 2017, from which we updated the number of the hosts to 312 fish species and 11 non-fish species, which is quite unusual among helminths. The AFT has spread to all but one continent (Antarctica). The highest number of records are from North America, followed by Asia and Europe. A key feature of its invasive success is its broad environmental tolerance., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A taxonomic study of monozoic cestodes of the genus Glaridacris Cooper, 1920 (Cestoda: Caryophyllidea), parasites of catostomid fishes in North America, confirmed artificial character of the genus which is split to 2 different, morphologically distinct, and not closely related genera. Glaridacris is newly circumscribed to include only 3 species, Glaridacris catostomi Cooper, 1920 (type species), Glaridacris terebrans ( Linton, 1893 ), and Glaridacris vogei Mackiewicz, 1976 , which are characterized by an elongate body, a cuneiloculate or wedge-shaped scolex with 6 shallow loculi, male and female gonopores at a distance from each other, follicular ovary, and circum-medullary vitelline follicles (lateral and median). A new genus, Pseudoglaridacris n. gen., is proposed to accommodate 3 species characterized by a shorter body, a bothrioloculodiscate scolex with a pair of deeper median bothria and 2 shallower loculi, male and female gonopores close together, non-follicular ovary, and with only lateral vitelline follicles. The species are: Pseudoglaridacris laruei ( Lamont, 1921 ) n. comb. (type species), Pseudoglaridacris confusa (Hunter, 1929) n. comb., and Pseudoglaridacris oligorchis ( Haderlie, 1953 ) n. comb. An annotated list of all species of both genera, with data on their hosts and distribution and keys to their identification, is provided.

Broad tapeworms (Cestoda: Diphyllobothriidea) are the principal agents of widespread food-borne cestodosis. Diphyllobothriosis and diplogonoporosis, caused by members of the genera Diphyllobothrium, Diplogonoporus and Adenocephalus, are the most common fish cestodoses with an estimated 20million people infected worldwide, and has seen recent (re)emergences in Europe due to the increasing popularity of eating raw or undercooked fish. Sparganosis is a debilitating and potentially lethal disease caused by the larvae of the genus Spirometra, which occurs throughout much of the (sub)tropics and is caused by the consumption of raw snakes and frogs, and drinking water contaminated by infected copepods. Both diseases are caused by several species, but the frequency by which the transition to humans has occurred has never been studied. Using a phylogenetic framework of 30 species based on large and small nuclear ribosomal RNA subunits (ssrDNA, lsrDNA), large subunit mitochondrial ribosomal RNA (rrnL) and cytochrome c oxidase subunit I (cox1), we hypothesize that humans have been acquired asaccidental hosts four times across the tree of life of diphyllobothriideans. However, polytomies prevent an unambiguous reconstruction of the evolution of intermediate and definitive host use. The broad host spectrum and the frequency with which switching between major host groups appears to have occurred, may hold the answer as to why accidental human infection occurred multiple times across the phylogeny of diphyllobothriideans. In this study Diplogonoporus is determined to be the junior synonym of Diphyllobothrium. Furthermore, we divide the latter polyphyletic genus into (i) the resurrected genus Dibothriocephalus to include freshwater and terrestrial species including Dibothriocephalus dendriticus, Dibothriocephalus latus and Dibothriocephalus nihonkaiensis as the most common parasites of humans, and (ii) the genus Diphyllobothrium to accommodate parasites from cetaceans including the type species Diphyllobothrium stemmacephalum and Diphyllobothrium balaenopterae n. comb. known also from humans. The non-monophyletic aggregate of marine species from seals is provisionally considered as incertae sedis., (Copyright © 2017 Australian Society for Parasitology. All rights reserved.)

The freshwater fish faunas of the Palaearctic and Nearctic regions show similarities but also notable differences, resulting in diverse distributions of their parasites. Relatively few parasite species occur in both regions and fewer still have been examined using molecular data. We report a rare example of 'amphi-Pacific' distribution, involving the common Palaearctic parasite, the caryophyllidean cestode Caryophyllaeides fennica (Schneider, 1902), in the chiselmouth Acrocheilus alutaceus Agassiz and Pickering, 1855, an endemic cyprinid in northwestern Nearctic, Oregon. Available information on nonnative fish species in Oregon suggests that the parasite is native to the area and not introduced. Molecular data (18S ribosomal [r]DNA, 28S rDNA, internal transcribed spacer 2, and cytochrome c oxidase subunit 1 gene) indicate very little genetic divergence between representatives from the Palaearctic and Nearctic, and possibly a relatively more recent colonization of the Nearctic region by this cestode via the Beringian land bridge. This is remarkable considering that Acrocheilus has reportedly been in Oregon since the Miocene.

Tapeworms of the genus Caryophyllaeus Gmelin, 1790 (Caryophyllidea: Caryophyllaeidae), common parasites of cyprinid fishes, are reviewed and taxonomic status of 42 nominal taxa that have been placed in the genus during its long history is clarified. The following seven species occurring in the Palaearctic Region are recognised as valid: C. laticeps (Pallas, 1781), C. auriculatus (Kulakovskaya, 1961), C. balticus (Szidat, 1941) comb. n. (syn. Khawia baltica Szidat, 1941), C. brachycollis Janiszewska, 1953, C. fimbriceps Annenkova-Chlopina, 1919, C. syrdarjensis Skrjabin, 1913, and newly described Caryophyllaeus chondrostomi sp. n. (= C. laticeps morphotype 4 of Bazsalovicsová et al., 2014) from common nase, Chondrostoma nasus (Linnaeus), found in Austria and Slovakia. The new species differs by the paramuscular or cortical position of preovarian vitelline follicles, a large, robust body (up to 64 mm long), conspicuously long vas deferens, flabellate scolex with small wrinkles on the anterior margin, and anteriormost testes located in a relatively short distance from the anterior extremity. Caryophyllaeus kashmirenses Mehra, 1930 and Caryophyllaeus prussicus (Szidat, 1937) comb. n. are considered to be species inquirendae, C. truncatus von Siebold in Baird, 1853 and C. tuba von Siebold in Baird, 1853 are nomina nuda. Data on the morphology, host spectra, distribution and known life-cycles of valid species are provided. Phylogenetic interrelations of four species of the genus including its type species and newly described C. chondrostomi were assessed based on an analysis of sequences of lsrDNA and cox1. A key to identification of all valid species of Caryophyllaeus is also provided.

Cichlidocestus n. gen. is proposed to accommodate 2 new species of proteocephalidean cestodes, Cichlidocestus gillesi n. sp. from Cichlasoma amazonarum in Peru (type species) and Cichlidocestus janikae n. sp. from Hypsophrys nicaraguensis (all Perciformes: Cichlidae) in Costa Rica. The new genus is unique among all but 1 proteocephalidean genera in the position of the ovary that occupies the middle and posterior thirds of the median region of proglottids (vs. the ovary in the posterior third of proglottids near their posterior margin in all but 1 remaining taxa). In addition, Cichlidocestus is typified by the presence of a voluminous, spherical, internal seminal vesicle, several pairs of ventral excretory canals in the medulla, a pyramidal, quadrilobed scolex with an apical muscular sucker, and the posterior extent of the testes that may reach almost to the posterior margin of proglottids. The new genus shares the position of the ovary and its extension with Sciadocephalus (also a parasite of cichlids in the Neotropics as the new taxon); in all remaining proteocephalideans the ovary occupies the posterior third only. Sciadocephalus differs from Cichlidocestus by a different morphology of the scolex, which possesses an umbrella-like metascolex that is markedly wider than the strobila, the number of ventral osmoregulatory canals, and development of the uterus, which forms capsule-like formations filled with eggs in Sciadocephalus megalodiscus (vs. simple lateral diverticula in Cichlidocestus spp.). Both new species of Cichlidocestus can be easily distinguished from one another by the anterior extent of the poral vitelline follicles (anterior to the cirrus-sac, i.e., preporal, in C. gillesi vs. posterior, i.e., only postporal in C. janikae), size of the eggs (diameter of the external layer of the embryophore of C. gillesi 30-33 μm vs. 44-46 μm in C. janikae), and the number of uterine lateral diverticula (16-21 on 1 side in C. gillesi vs. only 8-12 in C. janikae) and the testes (37-46 in C. gillesi vs. 63-74 in C. janikae). Based on a phylogenetic analysis of the 28S rRNA gene (lsrDNA) sequences, C. gillesi forms a lineage sister to S. megalodiscus, thus supporting the morphological similarity of both genera that occur in fishes of the same family in the same zoogeographical region.

The parasite fauna of loaches (Cypriniformes: Cobitoidea), a group of small bottom-dwelling freshwater fishes with a mostly Eurasian distribution, remains a largely unknown quantity. Here we revise the taxonomy of tapeworms of the genus Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae) that had been found in loaches from the Palaearctic Region (Central Europe, Japan and Russia [Primorsky Region]). Molecular phylogenetic analysis based on two nuclear (ssr- and lsrDNA) and two mitochondrial genes (cox1 and rrnL) revealed a monophyletic group consisting of four valid species nesting within the Proteocephalus-aggregate: (i) Proteocephalus sagittus (Grimm, 1872) from Barbatula barbatula (Europe, Russia and Tajikistan), (ii) Proteocephalus demshini n. sp. from Barbatula toni (Russian Far East - Primorsky Region), (iii) Proteocephalus midoriensis Shimazu, 1990 from Lefua echigonia (Japan) and L. costata (Russia) (new host and geographical record), and (iv) Proteocephalus misgurni n. sp. from Misgurnus anguillicaudatus (Russia; Primorsky Region). Proteocephalus sagittus and P. demshini, and P. midoriensis and P. misgurni were recovered as sister taxa, respectively. Proteocephalus sagittus and P. demshini are characterized by having proglottids that are wider than long, an elongate to pyriform cirrus-sac and the vitelline follicles that form wide lateral bands. Proteocephalus midoriensis and P. misgurni are characterized by having proglottids that are more elongate and an ovoid to almost spherical cirrus-sac and the vitelline follicles forming narrow lateral bands. Proteocephalus demshini differs from P. sagittus in the posterolateral extent of the vitelline follicles, whereas P. misgurni can be distinguished from P. midoriensis mainly by the relative size of the ovary, posterior extent of the vitelline follicles and width of the scolex. Unlike most species of the Proteocephalus-aggregate that possess an apical sucker, all species from loaches are devoid of any apical organ. The existence of two new species in loaches from the Primorsky Region of Russia indicates high endemism of fish parasites in this region. A key to the identification of recognized species from loaches is provided., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Biological invasions represent a serious threat for aquaculture because many of introduced parasites may negatively affect the health state of feral and cultured fish. In the present account, the invasive tapeworm Atractolytocestus huronensis Anthony, 1958 (Cestoda: Caryophyllidea), which was originally described from North America and has been introduced to Europe including the British Isles with its specific host, common carp (Cyprinus carpio L.), is reported from Africa for the first time. Its recent introduction to South Africa, where it was found in four localities where common carp is cultured, is another evidence of insufficient prophylactic measures and inadequate veterinary control during transfers of cultured fish, especially common carp, between continents. Together with the Asian fish tapeworm, Bothriocephalus acheilognathi, A. huronensis is another fish tapeworm with ability to spread throughout the globe as a result of man-made introductions of its fish hosts.

Background: The genus Diplostomum (Platyhelminthes: Trematoda: Diplostomidae) is a diverse group of freshwater parasites with complex life-cycles and global distribution. The larval stages are important pathogens causing eye fluke disease implicated in substantial impacts on natural fish populations and losses in aquaculture. However, the problematic species delimitation and difficulties in the identification of larval stages hamper the assessment of the distributional and host ranges of Diplostomum spp. and their transmission ecology., Methods: Total genomic DNA was isolated from adult worms and shotgun sequenced using Illumina MiSeq technology. Mitochondrial (mt) genomes and nuclear ribosomal RNA (rRNA) operons were assembled using established bioinformatic tools and fully annotated. Mt protein-coding genes and nuclear rRNA genes were subjected to phylogenetic analysis by maximum likelihood and the resulting topologies compared., Results: We characterised novel complete mt genomes and nuclear rRNA operons of two closely related species, Diplostomum spathaceum and D. pseudospathaceum. Comparative mt genome assessment revealed that the cox1 gene and its 'barcode' region used for molecular identification are the most conserved regions; instead, nad4 and nad5 genes were identified as most promising molecular diagnostic markers. Using the novel data, we provide the first genome wide estimation of the phylogenetic relationships of the order Diplostomida, one of the two fundamental lineages of the Digenea. Analyses of the mitogenomic data invariably recovered the Diplostomidae as a sister lineage of the order Plagiorchiida rather than as a basal lineage of the Diplostomida as inferred in rDNA phylogenies; this was concordant with the mt gene order of Diplostomum spp. exhibiting closer match to the conserved gene order of the Plagiorchiida., Conclusions: Complete sequences of the mt genome and rRNA operon of two species of Diplostomum provide a valuable resource for novel genetic markers for species delineation and large-scale molecular epidemiology and disease ecology studies based on the most accessible life-cycle stages of eye flukes.

Two genera of caryophyllidean cestodes, Monobothrium Diesing, 1863 and Promonobothrium Mackiewicz, 1968 , from cypriniform fishes (cyprinids and suckers) in the Holarctic Region, are revised using morphological and molecular evidence. Monobothrium, which includes morphologically distinct species that occur in European cyprinids (Cyprinidae) and North American suckers (Catostomidae), is separated into 3 genera. Monobothrium becomes monotypic and is represented by its type species, Monobothrium wageneri Nybelin, 1922 , which occurs in European tench, Tinca tinca (Cyprinidae). Monobothrium auriculatum Kulakovskaya, 1961 from Leuciscus danilevskii (Cyprinidae) in the Ukraine, is tentatively transferred to Caryophyllaeus Gmelin, 1790 as Caryophyllaeus auriculatus ( Kulakovskaya, 1961 ) n. comb. because it possesses morphological characteristics considered to be typical of Caryophyllaeus but which are absent in Monobothrium (shape of the scolex, presence of a seminal receptacle, short neck, and absence of a large, muscular papilla surrounding the large gonopores). The 5 remaining Monobothrium species from suckers in North America are transferred to Promonobothrium based on shared morphological features and molecular data. Species of Promonobothrium differ from M. wageneri by having an external seminal vesicle (absent in M. wageneri), the absence of postovarian vitelline follicles in North American species (present in M. wageneri), and a scolex that is digitiform papillate, loculopapillate, or loculotruncate, i.e., equipped with weak loculi and a terminal introvert (vs. claviform, bluntly ended, with 6 weak, shallow, longitudinal grooves in M. wageneri). Phylogenetic analysis of nuclear ribosomal RNA genes ssr- and lsrDNA placed Promonobothrium minytremi within a clade of 3 of the 5 North American Monobothrium species. The position of M. wageneri, although distinct from the remaining Monobothrium species, is unresolved within the Caryophyllidea. This study further supports the pattern that the biogeography of caryophyllidean taxa is generally constrained by host and continental association.

Molecular phylogenetic analysis of an extensive collection of monozoic tapeworms of the genus Paracaryophyllaeus Kulakovskaya, 1961 (Cestoda: Caryophyllidea), parasites of loaches (Cypriniformes: Cobitidae) in Eurasia, has revealed cryptic species diversity within this long-time monotypic genus, especially in the Paracaryophyllaeus gotoi (Motomura, 1927) species complex [syn. Paracaryophyllaeus dubininorum (Kulakovskaya, 1961); type species]. Three independent, well-supported clades were discovered on the basis of molecular data: (i) specimens from Misgurnus anguillicaudatus and Cobitis lutheri from China, Russian Far East and Japan - called herein P. cf. gotoi 1, which may be conspecific with P. gotoi (Motomura, 1927), although in the absence of sequence data for P. gotoi from its type locality (basin of the River Kumkan in Korea), no certain inferences about their identity can currently be made; (ii) specimens from M. anguillicaudatus from China and Japan - P. cf. gotoi 2, which are morphologically indistinguishable from those of P. cf. gotoi 1; and (iii) morphologically distinct tapeworms from the endemic loach Cobitis bilseli from southwestern Turkey (Beyşehir Lake), which are described herein as a new species. Paracaryophyllaeus vladkae Scholz, Oros and Aydoğdu n. sp. differs from the remaining species of the genus in the following characteristics: the testes begin anterior to the first vitelline follicles (versus posterior), the body is short and robust (versus more elongate and slender), and the scolex is wide, rounded or apically tapered (versus claviform to truncate). Species composition of the genus, host specificity of species and geographical distribution are briefly discussed., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Molecular analysis of an extensive specimen collection of morphologically distinct tapeworms of the genus Caryophyllaeus Gmelin, 1790 (Cestoda: Caryophyllidea), parasites of cyprinid fishes in the Palaearctic Region, brought evidence of host-related plasticity in critical morphological characters widely used for species circumscription and classification of these tapeworms. The results obtained here do not support the traditionally used morphological concept of species-defining characters of the order Caryophyllidea Carus, 1863, especially due to high morphological plasticity of the scolex and the anterior end of the body. Several morphotypes within both Caryophyllaeus laticeps (Pallas, 1781) and Caryophyllaeus brachycollis Janiszewska, 1953 generally corresponding to different hosts and geographical regions, were recognised likely suggesting host- and geography-related intraspecific morphological variability. Genetic data confirmed euryxenous host specificity of both species, most profoundly C. laticeps, but did not support the existence of cryptic species. In fact, some of the fish hosts may harbour both of the congeneric species including several of their respective morphotypes. The pattern of morphological and genetic divergence observed in both cestode species studied indicates a scenario of possible host range extensions and subsequent parasite diversification. If molecular sequence variability and host-related morphological polymorphism are confirmed in other groups of monozoic cestodes, it may complicate species identification and straightforward classification of these parasites.

Recent molecular phylogenetic studies on fish tapeworms of the genus Caryophyllaeus Gmelin, 1790 (Cestoda: Caryophyllidea), parasites of cyprinid fishes in the Palaearctic Region, have revealed unexpected phenotypic plasticity that seems to be related to definitive hosts. In the present paper, Caryophyllaeus brachycollis Janiszewska, 1953 is redescribed and its two morphotypes are circumscribed on the basis of newly-collected specimens. Morphotype 1 from barbels [Barbus spp. including the type-host Barbus barbus (L.); Barbinae] and chubs (Squalius spp.; Leuciscinae) is characterised by a more robust body with spatulate scolex, which is only slightly wider than a very short neck region, and the anterior position of the testes and vitelline follicles, which begin immediately posterior to the scolex. Specimens of Morphotype 2 from breams (Abramis spp., Ballerus spp. and Blicca spp.; Abraminae), which have been previously misidentifed as Caryophyllaeus laticeps (Pallas, 1781), possess a more slender body with a flabellate scolex, which is much wider than a long neck, and the first testes begin at a considerable distance posterior to the first vitelline follicles. Despite conspicuous differences in the scolex morphology and the anterior extent of the testes and vitelline follicles, both morphotypes are identical in the morphology of the posterior end of the body, in particular that of the cirrus-sac, which is large, thick-walled, elongate-pyriform, and contains a long cirrus, and in the distribution of the vitelline follicles, which surround medially vas deferens near the cirrus-sac. A specimen of Morphotype 1 from B. barbus from the Argens River, France, is designated as neotype of C. brachycollis. The presence of phenotypic plasticity in morphological characteristics previously used for differentiation of species of Caryophyllaeus may confound species identification, which is crucial for biodiversity, ecological and evolutionary studies. To avoid these potential problems, combination of morphological and molecular data is strongly recommended.

Khawia abbottinae sp. n. is described from the Chinese false gudgeon, Abbottina rivularis (Basilewsky) (Cyprinidae: Gobioninae), from the Yangtze River basin in China. The new species can be distinguished from the congeneric species mainly by the arrangements of the testes, which form two longitudinal bands (other congeneric species have the testes irregularly scattered throughout the testicular region) and their number (at maximum 85 testes versus at least 160 in the other Khawia spp.), and the morphology of the scolex, which varies from cuneiform to widely bulbate scolex, being separated from the remaining body by a short neck and possessing a smooth, blunt or rounded anterior margin. Other typical features of K. abbottinae are its small size (total length less than 1.5 cm) and body shape, with the maximum width at its first third. The distinct status of the new species was confirmed by molecular data (ssrDNA and ITS1 sequences). Phylogenetic analyses revealed a close relationship of the new species with K. rossittensis (Szidat, 1937) and K. parva (Zmeev, 1936), parasites of crucian carp and goldfish (Carassius spp.), but both species markedly differ from K. abbottinae in their morphology. Until now, five valid species of Khawia (K. abbottinae, K. japonensis, K. rossittensis, K. saurogobii and K. sinensis) have been reported from China.

The poorly known proteocephalidean cestode Macrobothriotaenia ficta (Meggitt, 1931) from the sunbeam snake Xenopeltis unicolor (Ophidia: Xenopeltidae) is redescribed on the basis of re-examination of its type specimens from Burma (Myanmar), and vouchers from Thailand and Vietnam. The peculiar morphology of the scolex, which is formed by four pedunculate lobe-bearing pincer-shaped suckers, is described for the first time using scanning electron microscopy. In scolex morphology, M. ficta closely resembles phyllobothriidean cestodes, parasites of elasmobranchs. However, this similarity does not reflect phylogenetic relatedness of these cestodes but instead presents an example of convergent morphological evolution of attachment organs of unrelated groups of cestodes that parasitize different groups of vertebrates. Besides scolex morphology, the genus is characterised by the possession of a very large cirrus-sac, which may reach up to the midline of proglottides, few testes (less than 60), vitelline follicles limited to the dorsal side of proglottides, a large vaginal sphincter, and eggs with a three-layered embryophore covered with rounded projections. Numerous errors in the diagnosis of M. ficta, which appeared in the literature as a result of uncritical compilation of data without examination of original material, are corrected. Multilocus phylogenetic analysis of nuclear ribosomal RNA genes ssr- and lsr-DNA and mitochondrial genes rrnL and cox1 place this species among other snake-parasitizing proteocephalideans of the genus Ophiotaenia. The convergent evolution of scolex morphology across distantly related taxa is discussed.

Australotaenia de Chambrier et de Chambrier, 2010 has been proposed to accommodate two species of proteocephalidean cestodes from hylid frogs (Litoria spp.) in Australia. Recently, apparently congeneric cestode, for which the name A. bunthangi sp. n. is proposed, was found in the homalopsid snake Enhydris enhydris (Schneider) (Serpentes: Homalopsidae) from South-East Asia (Cambodia). This finding indicates a much wider range of definitive hosts of species of this genus, i.e. amphibians and reptiles, which is exceptional among proteocephalideans. Postcyclic parasitism, i.e. predation of the definitive host infected with sexually mature parasites, cannot be excluded but does not seem to be probable. In addition, the occurrence of A. bunthangi in the former Indochina extends the range of the geographical distribution of the genus to another zoogeographical region. The new species differs from both species of Australotaenia in the relative size of an apical organ, the diameter of which equals to that of suckers (versus much smaller in the remaining species, in which the width of the apical organ represents less than 2/3 of the diameter of the suckers), much smaller scolex and suckers (width 150 microm and diameter of suckers 50-55 microm versus 245-420 microm and 100-140 microm, respectively), and longer body (224 mm versus 57-121 mm). In addition, A. bunthangi differs from A. hylae (Johnston, 1912) (type-species of the genus) by the number of testes (46-64 versus 74-106 in A. hylae) and by the ovary width/proglottis width ratio (55-65% versus 68-71% in A. hylae). Australotaenia bunthangi differs from A. grobeli de Chambrier et de Chambrier, 2010 by relative size of the cirrus-sac (its length represents 18-24% of the width of the proglottis versus 27-33% in A. grobeli) and by the diameter of the embryophore (25-27 microm versus 18-23 microm in A. grobeli).

A new caryophyllidean cestode is described from barbs Puntius spp. (Cypriniformes: Cyprinidae), with P. sophore (Hamilton) as its type-host, in the Ganges and Brahmaputra river basins in India and Bangladesh, and a new genus, Lobulovarium n. g., is proposed to accommodate it. The genus belongs to the Lytocestidae because its vitelline follicles are situated in the cortex. It is typified by: (i) a peculiar ovary, which is roughly H-shaped, but with asymmetrical, irregular lobes on its ventral and dorsal sides; (ii) an extensive vitellarium formed by numerous vitelline follicles scattered throughout the cortex; (iii) a long, conical postovarian part of the body with numerous vitelline follicles; (iv) a broadly digitate scolex with a slightly protrusible central cone; (v) a single gonopore (male and female genital ducts open via a single pore and a common genital atrium is absent); and (vi) a small number of testes (< 60). Molecular data (partial sequences of the lsrDNA) indicate that Lobulovarium longiovatum n. sp. belongs among the most basal caryophyllidean cestodes, being unrelated to species from siluriform catfishes in the Indomalayan region. Paracaryophyllaeus osteobramensis (Gupta & Sinha, 1984) Hafeezullah, 1993 (syn. Pliovitellaria osteobramensis Gupta & Sinha, 1984) from another cyprinid fish, Osteobrama cotio (Hamilton), in Uttar Pradesh, India, is tentatively transferred to Lobulovarium as L. osteobramense (Gupta & Sinha, 1984) n. comb. It differs from L. longiovatum by having much smaller eggs (length <50 μm versus >90 μm in L. longiovatum), which are spherical (length/width ratio 1:1 versus 2.5-3:1 in the new species), and the presence of vitelline follicles alongside the ovarian lobes (almost completely absent in L. longiovatum).

A new proteocephalidean cestode is described from spot pangasius, Pangasius larnaudii (Siluriformes: Pangasiidae), from Tonle Sap Lake in Cambodia and a new genus, Pangasiocestus , is proposed to accommodate it. The genus is placed in the Gangesiinae because its scolex possesses a large rostellum-like apical organ and its genital organs (testes, ovary, vitellarium, and uterus) are situated in the medulla, with some vitelline follicles paramuscular. Pangasiocestus romani n. gen. and n. sp., the type and only species of the new genus, is characterized mainly by its rosette-like scolex composed of 4 lobes bearing a small sucker in their center, and the apical part with a large, discoidal, rostellum-like apical organ devoid of hooks, by weakly developed inner longitudinal musculature formed by very few isolated muscle fibers, uneven size of testes in immature and mature proglottids, with lateral testes smaller and more dense than median ones, by very narrow lateral bands of vitelline follicles, formed usually by single follicles, and by the vagina anterior to the cirrus sac. This is the first proteocephalidean cestode from a pangasiid catfish identified to the species level (proteocephalidean cestodes from 3 Pangasius spp. reported in an unpublished account from Vietnam, misidentified as Proteocephalus osculatus (Goeze, 1782) [ =  Glanitaenia osculata ], are not considered).

Sequence structure of complete internal transcribed spacer 1 and 2 (ITS1 and ITS2) of the ribosomal DNA region and partial mitochondrial cytochrome c oxidase subunit I (cox1) gene sequences were studied in the monozoic tapeworm Atractolytocestus sagittatus (Kulakovskaya et Akhmerov, 1965) (Cestoda: Caryophyllidea), a parasite of common carp (Cyprinus carpio carpio L.). Intraindividual sequence diversity was observed in both ribosomal spacers. In ITS1, a total number of 19 recombinant clones yielded eight different sequence types (pairwise sequence identity, 99.7-100%) which, however, did not resemble the structure typical for divergent intragenomic ITS copies (paralogues). Polymorphism was displayed by several single nucleotide mutations present exclusively in single clones, but variation in the number of short repetitive motifs was not observed. In ITS2, a total of 21 recombinant clones yielded ten different sequence types (pairwise sequence identity, 97.5-100%). They were mostly characterized by a varying number of (TCGT)(n) repeats resulting in assortment of ITS2 sequences into two sequence variants, which reflected the structure specific for ITS paralogues. The third DNA region analysed, mitochondrial cox1 gene (669 bp) was detected to be 100% identical in all studied A. sagittatus individuals. Comparison of molecular data on A. sagittatus with those on Atractolytocestus huronensis Anthony, 1958, an invasive parasite of common carp, has shown that interspecific differences significantly exceeded intraspecific variation in both ribosomal spacers (81.4-82.5% in ITS1, 74.4-75.2% in ITS2) as well as in mitochondrial cox1, which confirms validity of both congeneric tapeworms parasitic in the same fish host.

The ultrastructure of spermiogenesis and mature spermatozoon in Lytocestus indicus (Cestoda: Lytocestidae) is described; this is the first representative of this group of monozoic, presumably most basal, tapeworms (Eucestoda) from the Indomalayan region to be documented in this manner. Similarly, as in other caryophyllideans, its spermiogenesis involves the formation of a conical differentiation zone with 2 centrioles associated with striated roots and an intercentriolar body. In the course of the process, 1 of the centrioles develops a free flagellum, which fuses with a cytoplasmic protrusion, whereas the other remains oriented in a cytoplasmic bud. Spermiogenesis is also characterized by the presence of electron-dense material in the early stages of spermiogenesis and a slight rotation of the flagellar bud. The mature spermatozoon of L. indicus is a filiform cell tapered at both extremities that lacks mitochondria; its nucleus has parallel disposition to the axoneme and does not reach up to the posterior extremity of the spermatozoon, which is typical for spermatozoa of the type III pattern. The new data confirm that caryophyllideans share the same type of spermiogenesis that is considered to be plesiomorphic in the Eucestoda. The existing information on spermatological ultrastructure of 8 members for 3 of 4 caryophyllidean families from different host groups (cyprinids and catostomids, both Cypriniformes, and mochokids and clariids, both Siluriformes) from 4 zoogeographical regions (Palearctic, Neotropic, Ethiopian, and Indomalayan regions) demonstrates great uniformity in spermiogenesis and sperm ultrastructure, which does not reflect different taxonomic position of the species studied.

Larvae of the cyclophyllidean tapeworms Paradilepis scolecina (Rudolphi, 1819), Neogryporhynchus cheilancristrotus (Wedl, 1855) and Valipora campylancristrota (Wedl, 1855), are described from British freshwater fish. The morphometrics of the rostellar hooks, infection characteristics and host ranges of these parasites from fisheries in England and Wales are presented. Difficulties in the detection, handling and identification of these tapeworms are highlighted, and may in part explain the paucity of records from Britain. Tissue digestion was shown to be a useful technique for the examination of these parasites, providing clear and consistent preparations of the rostellar hooks for measurement. The pathological changes caused by P. scolecina to the liver of wild tench, Tinca tinca, are detailed for the first time. Tapeworms located in the hepatic parenchyma and pancreatic tissues caused little pathological damage and invoked only mild inflammatory responses. The small size of these tapeworms and their encapsulation within host tissues appear to limit the severity of pathology, compared with parasites that insert their rostellum during attachment.

Ophiotaenia bungari n. sp. (Cestoda: Proteocephalidea) is described from the intestine of the banded krait Bungarus fasciatus (Schneider) (Ophidia: Elapidae) in Vietnam. The new species differs from all but three Ophiotaenia species parasitic in Asian reptiles in the possession of a glandular apical organ. It differs from O. andersoni Jensen, Schmidt & Kuntz, 1983 in the position of the vagina in relation to the cirrus-sac (anterior and posterior in O. bungari versus anterior only in the latter species), in the cirrus-sac/proglottis width ratio (29-38 versus 50%) and by having more testes (100-150 versus 42-116 in O. andersoni); from O. chattoraji Srivastava, 1980 in the number of uterine diverticula (50-65 versus 10-26) and in the cirrus-sac/proglottis width ratio (29-38 versus 22%); and from O. rhabdophidis (Burt, 1937) by having more uterine diverticula (50-65 versus 30-45), by the cirrus-sac/proglottis width ratio (29-38 versus 20-25%) and by the width of the scolex (360-420 versus 130-187 μm). The taxonomic importance of the relative size of the ovary (i.e. the ratio of the ovarian size in relation to that of the entire proglottis), a character previously not used in the systematics of proteocephalidean cestodes, is discussed. Comparison of measurements of all of the nominal species of Ophiotaenia La Rue, 1911 and Proteocephalus Weinland, 1858 (c.135 species) has shown that the ovary of species parasitic in snakes in the Americas, Africa, Asia and Australia is not only considerably smaller than that of congeneric species from European hosts, but also smaller than in all species of Proteocephalus parasitic in teleost fishes throughout the world.

Monobothrium wageneri is a monozoic caryophyllidean tapeworm of tench Tinca tinca. The pathological changes caused by this parasite within the intestinal tract of wild tench are described for the first time. Parasites were found attached to the anterior third of the intestine in tight clusters comprising up to 109 tapeworms. Infection was associated with the formation of raised inflammatory swellings surrounding the parasites. This host response, combined with the deep penetration of the scolex into the gut wall, formed a very firm seat of parasite attachment. Histopathological changes were characterised by a pronounced fibrogranulomatous lesion that extended through all layers of the intestine. This was accompanied by haemorrhage, oedema, necrosis and degeneration of the muscularis. A marked eosinophilic interface layer between the scolex of the tapeworm and gut wall indicated intimate host-parasite contact. Ultrastructural examinations revealed coniform spinitriches covering the neck and lateral sides of the scolex and capilliform filitriches present on the apical end of the scolex. Numerous glandular cytons (tegumental glands) were recorded throughout the scolex tegument. Large numbers of secretory granules discharged from the glands through a network of processes onto the scolex surface were consistent with distancing the cellular responses of the host. Observations of severe inflammatory lesions, partial intestinal occlusion and the potential for intestinal perforation represent important pathological changes that are consistent with loss of normal gut function. The lesions associated with the attachment of M. wageneri are more severe than those recorded for any other tapeworm of British freshwater fish.

The proteocephalidean tapeworm, Corallobothrium solidum, type species of the genus, is redescribed on the basis of the examination of its type specimens and extensive material recently collected from Malapterurus electricus (type host). Some morphological characteristics of taxonomic importance are reported for the first time, such as the presence of semispherical (U-shaped) sphincters on the external (outer) margin of the suckers, a vaginal sphincter, a well-developed seminal receptacle, and a unique morphology of the eggs. Corallobothrium solidum differs from the 2 remaining species of the genus, both parasitic in channel catfishes (Ictaluridae), in its scolex shape, morphology of its suckers, presence of longitudinal and transverse grooves on the body surface, dense network of excretory canals in the apical part of the scolex, morphology of the eggs, and uterine development. The non-monophyletic nature of Corallobothrium is further supported by molecular data (partial sequences of the 28S rRNA gene) because C. solidum and the 2 remaining species from ictalurids do not form a monophyletic assemblage. Therefore, Essexiella n. gen. is proposed to accommodate Essexiella fimbriatum new comb. (type and only species; syn. Corallobothrium fimbriatum) from channel catfish. Essexiella n. gen. differs from Corallobothrium, Megathylacoides, and Megathylacus by the absence of a sphincter in the suckers, from Corallotaenia by the shape of the scolex and the number and shape of proglottids, and from Paraproteocephalus by the structure of the uterus. The diagnosis of Corallobothrium, which becomes monotypic and restricted to electric catfishes in Africa, is emended. The remaining species of Corallobothrium, Corallobothrium parafimbriatum, is tentatively transferred to Corallotaenia as Corallotaenia parafimbriata n. comb., based on molecular data, small size of the strobila, and shape of the scolex.

A new genus, Ritacestus, is proposed to accommodate Ritacestus ritaii (Verma, 1926) comb. n. (syn. Proteocephalus ritaii), a parasite of the catfish Rita rita (Hamilton) in India. The new genus, which is placed in the Gangesiinae, is characterized by (i) a small, subspherical scolex formed by four large lobes separated from one another by longitudinal grooves, with a large, widely oval to pyriform rostellum-like apical organ, larger than suckers and possessing an apical hemispherical depression; (ii) paramuscular and cortical position of some vitelline follicles (most follicles are situated medullary); (iii) ventral and dorsal bands of vitelline follicles usually uninterrupted ventral to terminal genitalia and reaching to the posterior margin of proglottides; (iv) the vagina always anterior to the cirrus-sac; (v) a large size of the body (length up to 51 cm); and (vi) development of the uterus of type 2. In its morphology, especially shape of the scolex and apical organ, and paramuscular and cortical position of some vitelline follicles, Ritacestus resembles Postgangesia Akhmerov, 1969, but differs in the presence of a genital atrium (both genital pores of Postgangesia are separate), the anterior position of the vagina (almost always posterior in the latter genus), position of vitelline follicles in cross sections (dorsal and ventral bands in Ritacestus versus only a lateral band in the latter genus), and dorsal excretory canals indistinguishable in mature and gravid proglottides of R. ritaii (well developed in Postgangesia spp.). The type and only species of the genus, R. ritaii, is redescribed on the basis of new material from the type host from the Ganges River basin in India and its neotype is designated.

The stinging catfish Heteropneustes fossilis (Bloch) (Siluriformes: Heteropneustidae) has been reported to harbor as many as 19 species of caryophyllidean tapeworms (Cestoda) of 11 genera in tropical Asia (Indomalayan zoogeographical region). However, a critical review of the species composition has shown that only 1 species, Lucknowia fossilisi Gupta, 1961 (Lytocestidae), is a specific parasite of H. fossilis. Three other species, Djombangia penetrans Bovien, 1926 (syn., Djombangia caballeroi Sahay and Sahay, 1977 ), Pseudocaryophyllaeus ritai Gupta and Singh, 1983 (syn. Pseudocaryophyllaeus lucknowensis Gupta and Sinha, 1984 ), and Pseudocaryophyllaeus tenuicollis (Bovien, 1926) Ash, Scholz, Oros and Kar, 2011 (syn. P. mackiewiczi Gupta and Parmar, 1982 ), were found only once. Lucknowia fossilisi is redescribed on the basis of new material collected in West Bengal and voucher specimens from Maharashtra, India. A total of 9 species of Capingentoides, Lucknowia, Lytocestus, Pseudoadenoscolex, Pseudocaryophyllaeus, Pseudoheteroinverta, and Sukhapatae are newly synonymized with L. fossilisi and previous synonymies of 9 other species, proposed by Hafeezulah (1993), are confirmed. Generic diagnosis of Lucknowia Gupta, 1961 is amended. In addition, 1 species of Pseudobatrachus and 2 species of the monotypic genera Pseudoneckinverta and Sudhaena are invalidated as nomina nuda.

The invasive monozoic tapeworm Atractolytocestus huronensis, a specific parasite of common carp, was originally found and described in the North American continent. It has been introduced to Europe and reported in several countries in the last 15 years, as well. In the current study, tapeworms from one North American (USA) and five European localities (United Kingdom/UK, Slovakia, Hungary, Croatia, and Romania) were subjected to molecular analyses in order to determine the level of intrapopulation and intraspecific molecular variation and to assess interrelationships among American and European populations of the parasite. Partial sequences (672 bp) of the mitochondrial cytochrome c oxidase subunit I (cox1) revealed the presence of only two cox1 haplotypes, in accordance with the nonnative character of the populations. The first haplotype was common for all tapeworms from the Continental Europe (Slovakia, Hungary, Croatia, and Romania); no differences were determined either within or among respective A. huronensis populations. The second cox1 haplotype was characterized in all individuals from the USA and UK, indicating their close genetic relationship. Both haplotypes differed in three nucleotide positions (99.6% identity) which did not change the amino acid sequence. The cox1 data imply that introduction of the parasite to Europe was probably the result of two independent events directed to the UK and Continental Europe. The very close genetic relationship between British and American A. huronensis was reflected also by similar ribosomal internal transcribed spacer 2 (ITS2) sequence structure; considerable intragenomic ITS2 variability was detected in all individuals of both geographic populations. Divergent ITS2 copies were mostly induced by different numbers of short repetitive motifs within the sequences, allowing their assortment into two ITS2 variants.

Revision of monozoic cestodes (Caryophyllidea) parasitic in commercially important walking catfish Clarias batrachus (L.) in tropical Asia (Indomalayan zoogeographical region) was carried out, based on the evaluation of newly collected material from India, Indonesia, and Thailand, as well as a study of type specimens. Instead of the 59 nominal taxa of 15 genera from 3 caryophyllidean families previously described, only 8 species of the Lytocestidae are considered to be valid: Bovienia indica (Niyogi, Gupta and Agarwal, 1982) n. comb.; Bovienia raipurensis (Satpute and Agarwal, 1980) Mackiewicz, 1994; Bovienia serialis (Bovien, 1926) Fuhrmann, 1931; Djombangia penetrans Bovien, 1926; Lucknowia microcephala (Bovien, 1926) n. comb.; Lytocestus indicus (Moghe, 1925) Woodland 1926; Pseudocaryophyllaeus ritai Gupta and Singh, 1983; and Pseudocaryophyllaeus tenuicollis (Bovien, 1926) n. comb. All valid species are redescribed and SEM photomicrographs of their scolices and photomicrographs of their eggs are provided for the first time. Crescentovitus Murhar, 1963, Heeradevina Srivastav and Khare, 2005, Pseudobatrachus Pathak and Srivastav, 2005, Pseudobilobulata Srivastav and Lohia, 2002, Pseudoclariasis Pathak, 2002, and Pseudoinverta Pathak, 2002 are invalidated and 50 nominal species are newly synonymized, including 4 species described from other fish hosts. Taxonomic status of the remaining caryophyllidean taxa reported from C. batrachus (at least 6 taxa) could not be clarified because of the unavailability of their original descriptions. A key to identification of caryophyllidean tapeworms parasitic in C. batrachus is provided. To avoid current inflation of descriptions of invalid taxa, researchers are strongly encouraged to work only with well-fixed material; damaged, decomposed, or strongly flattened specimens should not be used for taxonomic studies, and type specimens must always be deposited in internationally recognized collections.