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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 caryophyllidean genus Archigetes Leuckart, 1878 is unique among all tapeworms in that its species can mature in invertebrate hosts (Oligochaeta), i.e., have a monoxenic (direct) life cycle. All five species were described as progenetic plerocercoids in oligochaetes and two of them also as adults from cypriniform fishes. Two species, A. sieboldi Leuckart, 1878 and A. iowensis Calentine, 1962, were found in North America in non-native common carp (Cyprinus carpio). A molecular study of caryophyllideans from the southern United States has revealed the occurrence of three new species in native freshwater fishes (Catostomidae, Ictiobinae): Archigetes loculotruncatus n. sp. from Ictiobus bubalus, I. niger and Carpiodes cyprinus is the largest representative of the genus and differs by a loculotruncate scolex. Archigetes megacephalus n. sp. from Ictiobus niger, I. bubalus and I. cyprinellus is characterised by a prominent, bothrioloculodiscate scolex. Archigetes vadosus n. sp. from I. bubalus is typified by a globular scolex with very shallow loculi; it differs from the closely related A. sieboldi in the shape of the body, with a distinct neck region and a scolex wider than the remaining body. Archigetes iowensis Calentine, 1962 becomes a junior synonym of Paraglaridacris limnodrili (Yamaguti, 1934). The generic diagnosis of Archigetes is amended and a key to identification of North American taxa is provided. Species of Archigetes and Paraglaridacris differ from each other most conspicuously in the structure of the ovary, which is follicular in Archigetes versus compact in Paraglaridacris., (© D. Uhrovič et al., published by EDP Sciences, 2022.)

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.

The biodiversity of freshwater ecosystems globally still leaves much to be discovered, not least in the trematode parasite fauna they support. Echinostome trematode parasites have complex, multiple-host life-cycles, often involving migratory bird definitive hosts, thus leading to widespread distributions. Here, we examined the echinostome diversity in freshwater ecosystems at high latitude locations in Iceland, Finland, Ireland and Alaska (USA). We report 14 echinostome species identified morphologically and molecularly from analyses of nad1 and 28S rDNA sequence data. We found echinostomes parasitising snails of 11 species from the families Lymnaeidae, Planorbidae, Physidae and Valvatidae. The number of echinostome species in different hosts did not vary greatly and ranged from one to three species. Of these 14 trematode species, we discovered four species (Echinoparyphium sp. 1, Echinoparyphium sp. 2, Neopetasiger sp. 5, and Echinostomatidae gen. sp.) as novel in Europe; we provide descriptions for the newly recorded species and those not previously associated with DNA sequences. Two species from Iceland (Neopetasiger islandicus and Echinoparyphium sp. 2) were recorded in both Iceland and North America. All species found in Ireland are new records for this country. Via an integrative taxonomic approach taken, both morphological and molecular data are provided for comparison with future studies to elucidate many of the unknown parasite life cycles and transmission routes. Our reports of species distributions spanning Europe and North America highlight the need for parasite biodiversity assessments across large geographical areas., (© C. Pantoja et al., published by EDP Sciences, 2021.)

Neopsilotrema n. g. (Digenea: Psilostomidae) and three new species of psilostomid digeneans are described from birds in North America and Europe: Neopsilotrema lakotae n. sp. from Aythya americana (Eyton) in North Dakota, USA, Neopsilotrema affine n. sp. from Aythya affinis (Eyton) in Minnesota, USA and Neopsilotrema lisitsynae n. sp. from Anas crecca L. in Kherson Region, Ukraine. Neopsilotrema n. g. shares a bipartite seminal vesicle with only three genera within the Psilostomidae, Psilotornus Byrd & Prestwood, 1969, Psilostomum Looss, 1899 and Grysoma Byrd, Bogitsh & Maples, 1961. The new genus differs from Psilotornus in the presence of a muscular pharynx and a massive ventral sucker; the location of the cirrus-sac in relation to the ventral sucker and more posterior location of ovary; the nature of the vitellarium (i.e. comprising large, compact follicles with small vitelline cells vs weakly defined follicles with large vitelline cells); a proportionately shorter forebody; and in parasitisation in anseriform (vs passeriform) birds. Differences between the new genus and Psilostomum comprise the shape of the body, the relative size of the suckers, somewhat longer forebody and a more anterior location of the testes. Neopsilotrema n. g. differs from Grysoma in the relative size of the suckers, the degree of development of prostatic cells, the nature of the vitellarium and the size of the eggs in relation to body length. The European species Neopsilotrema lisitsynae n. sp. is distinguished from its congeners in having a longer, narrower and distinctly more elongate body with a longer post-testicular region and anterior limits of the vitelline fields posterior to ventral sucker. The two North American forms, Neopsilotrema lakotae n. sp. and Neopsilotrema affine n. sp., are cryptic species with largely overlapping metrical data; these are distinguished by comparing genetic data. The phylogenetic hypotheses for the Psilostomidae developed from sequence data analyses based on partial 28S rDNA support the erection of the new genus and the distinction of the three new species. Grysoma marilae (Price, 1942) agrees more closely with the generic diagnosis of Neopsilotrema, especially in relation to the size and shape of the body, the relative length of the forebody and post-testicular field, the structure of the vitellarium, the location of the reproductive organs and the sucker ratio. Consequently, it is here transferred to the new genus as Neopsilotrema marilae (Price, 1942) n. comb.

Drepanocephalus auritus n. sp. is described based on specimens from the double-crested cormorant Phalacrocorax auritus (Lesson) in North America. The new species differs from its congeners in its very narrow, elongate body, long uterine field and widely separated testes. Sequences of the nuclear rRNA gene cluster, spanning the 3' end of the nuclear ribosomal 18S rRNA gene, internal transcribed spacer region (ITS1+5.8S gene+ITS2) and partial 28S gene (2,345 bp), were identical in specimens collected from North Dakota, Minnesota and Mississippi, USA. Sequences of the 651 bp long fragment of the mitochondrial cox1 gene exhibited very low intraspecific variability (< 1%). Comparisons of the newly-generated sequences with those available in the GenBank indicate that the sequences from North America published under the name D. spathans Dietz, 1909 in fact represent D. auritus n. sp.