Three new species of Rhabdias Stiles et Hassall, 1905 (Nematoda: Rhabdiasidae) parasitic in Ptychadena spp. (Amphibia: Anura: Ptychadenidae) and an identification key to Rhabdias spp. from Afrotropical anurans

Three new species of lung-dwelling nematodes are described from the frogs Ptychadena anchietae (Bocage), P. oxyrhynchus (Smith), and P. uzungwensis (Loveridge) in southern Africa. All three species are medium-sized species of Rhabdias Stiles et Hassall, 1905, with the thick-walled buccal capsules measuring 11-13 μm × 6-11 μm, consisting of longer anterior and shorter posterior parts. Rhabdias athos n. sp. and R. porthos n. sp. are characterised by the rounded anterior end of the body and the presence of short dilatation of the oesophagus at its mid-length. Rhabdias porthos n. sp. has distinct excretory glands which are absent in two other species. Rhabdias aramis n. sp. is characterised by the truncated anterior end and the slight constriction of the oesophagus at the level of its mid-length. Phylogenetic analysis based on ITS-28S rDNA sequences placed R. aramis n. sp. in the clade consisting of R. engelbrechti Kuzmin et al., 2017 from South Africa and Eurasian Rhabdias spp., while R. athos n. sp. and R. porthos n. sp. formed a sister group to that clade. Identification key to 14 Rhabdias spp. parasitic in anuran amphibians from the Afrotropical Realm is provided.

New host record, Sclerophrys regularis (Bufonidae), for Rhabdias africanus (Rhabdiasidae, ) based on molecular and morphological evidence

With diversity of hosts range, most identified nematode species still lack the crucial connection between morphological and molecular make-up, which is important for precisely classifying the specimens. The present study provides the complete description of Rhabdias africanus in the new host record, Sclerophrys regularis. Fifty toad specimens were collected, and a high prevalence of R. africanus infection (74%) was observed. Morphology and ultrastructure were observed using light and scanning electron microscopes. Morphological characteristics, including peculiarities of the head, the shape and position of the lips, and the number of labial papillae, were described. The length of the body, the esophageal length, the distance from an anterior end to the nerve ring, and the tail length were reduced in the studied samples relative to previously described specimens. Furthermore, some variable matrices that have not previously been described, e.g., ovarian part widening, the nerve ring and its location, and eggs with different stages of larvae, were included in the present study. Genus and species identification was confirmed by comparing partial 12S (619 bp) and ITS (878 bp) gene sequences to those of Rhabdias species deposited in GenBank. The studied species showed a 99.34% resemblance to R. africanus from South Africa. We assume our findings will aid in the molecular identification of adult and larval stages of this genus in amphibians. We strongly recommend further studies on the environmental factors that promote Rhabdias infection and transmission.

Phylogeography of Rhabdias spp. (Nematoda: Rhabdiasidae) collected from Bufo species in Honshu, Shikoku, and Kyushu, Japan including possible cryptic species

The genus Rhabdias Stiles & Hassall, 1905 comprises lung parasites of amphibians and reptiles worldwide. In Japan, 9 species have been recorded, including Rhabdias incerta Wilkie, 1930 which has been reported only in Bufo species. In this study, to assess the diversity of R. incerta, we performed molecular analyses of Rhabdias species sampled from three species/subspecies of Japanese toads namely Bufo japonicus, B. japonicus formosus, and B. torrenticola, collected in various regions of Honshu, Shikoku, and Kyushu, Japan. DNA sequence divergence was compared using mtDNA (COI) and nuclear DNA (28S) to identify possible cryptic species. Morphological analysis was performed through light microscopy and scanning electron microscopy (SEM). The results revealed that Bufo spp. serve as hosts for at least three Rhabdias species. Morphologically, most samples were identified as R. incerta but with a longer body and larger buccal cavity than originally described. Rhabdias incerta appears to be specific to the genus Bufo and is further subdivided into two or three phylogroups based on subspecies divisions and biogeography of their host. Some Rhabdias specimens collected in this study resemble R. tokyoensis Wilkie, 1930, parasitic in hosts from the order Caudata, which suggests host switching. Both molecular and morphological analyses suggested the presence of undescribed and cryptic Rhabdias species within toads collected in Japan. This study was the first to molecularly characterize Rhabdias species in Japan, including novel sequences of R. incerta and two undescribed species.

First record of Metapolystoma (Monogenea: Polystomatidae) from Boophis tree frogs in Madagascar, with the description of five new species

Although Madagascar has more than 350 frog species of which all but two are endemic to the island, the known polystome (Monogenea: Polystomatidae) diversity parasitizing Malagasy frogs is low, encompassing five species of Madapolystoma, one species of Kankana and one Metapolystoma. Investigating the parasite diversity of frog parasites at selected Malagasy localities led to the discovery of undescribed polystomes. Five treefrogs, Boophis albilabris, Boophis doulioti, Boophis luteus, Boophis madagascariensis and Boophis occidentalis were found to be infected and are reported here as hosts for new Metapolystoma species. Morphological investigation, combining examination of body length, haptor length, genital bulb width, genital crown diameter, genital spine number, genital spine length, ovary length, egg length, hamulus length, hamulus guard length and hamulus hook length, revealed five distinct morphotypes. Phylogenetic analysis and genetic divergences obtained for three of the five morphotypes, support the distinction of new species. Metapolystoma ansuanum n. sp. is described from B. luteus, Metapolystoma falcatum n. sp. from B. doulioti, Metapolystoma multiova n. sp. from B. occidentalis, Metapolystoma theroni n. sp. from B. madagascareniensis and Metapolystoma vencesi n. sp. from B. albilabris. Finally, although the validity of Metapolystoma as taxon is not fully resolved yet, the phylogenetic position of the described species and their morphology provide clear evidence for new metapolystome taxa.

A new species of Rhabdias (Nematoda: Rhabdiasidae), a lung parasite of Pseudopaludicola pocoto (Anura: Leptodactylidae) from north-eastern Brazil: description and phylogenetic analyses

Rhabdias pocoto n. sp. is herein described from the lungs of the swamp frog Pseudopaludicola pocoto Magalhães, Loebmann, Nogueira, Kokubum, Baptista, Haddad & Garda, 2014, from the Caatinga biome in the state of Ceará, in north-eastern Brazil. The new species is characterized by a body that dilates posteriorly, six small lips (protuberances) and two rounded lateral expansions of cuticular inflation on the anterior end, each containing an amorphous gland-like structure inside and a short and conical tail. Additionally, molecular analysis and comparison of the partial mitochondrial cytochrome c oxidase I sequence of R. pocoto n. sp. revealed genetic divergence between the new species and the sequences of Rhabdias spp. previously deposited in GenBank. Phylogenetic analysis grouped the new taxon into the R. pseudosphaerocephala species complex + R. glaurungi clade. The new discovery represents the 19th species of Rhabdias spp. described in the Neotropical region, the ninth in Brazil and the first species of Rhabdias found parasitizing South American frogs of the genus Pseudopaludicola, as well as the first Caatinga biome species of Rhabdias.

Molecular Diversity of Nematode Parasites in Afrotropical Reed Frogs (Hyperolius spp.)

The diversity of nematodes infecting amphibians is understudied in tropical Africa and unknown in Rwanda. Diversity assessment is hampered by the fact that species descriptions refer mostly to morphological features that are unlinked to DNA sequences of marker genes available in public databases. In this paper, we explore the abundance and diversity of parasitic nematodes in reed frogs Hyperolius kivuensis (n = 115), H. parallelus (n = 45) and H. viridiflavus (n = 100) collected in Rwanda. Five nematode species were identified morphologically as Orneoascaris chrysanthemoides, O. schoutedeni, Gendria leberrei, Aplectana chamaeleonis and Rhabdias collaris. Corresponding DNA sequences of 18S and COI genes were determined and subsequently deposited in GenBank. Aplectana chamaeleonis showed the highest prevalence (8.7%), but O. chrysanthemoides the highest mean intensity of infection (6.0) and largest number (24) of individuals in H. kivuensis. To the best of our knowledge, all amphibian hosts are new records for these nematode species, which are known to infect a wide range of amphibian and reptile species. Our findings suggest that nematode diversity is probably lower than previously assumed due to low host specificity. As morphological species identification is often challenging, our data facilitate molecular identification of adult and specifically larval nematodes found in amphibians of Sub-Saharan Africa.

Description and molecular characterisation of a new nematode species parasitic in the lungs of Strongylopus grayii (Smith) (Anura: Pyxicephalidae) in South Africa

Rhabdias delangei n. sp. (Nematoda: Rhabdiasidae) is described from the lungs of the clicking stream frog Strongylopus grayii (Smith) in the Western Cape Province of South Africa. The new species is characterised by the nerve-ring being located just posterior to the mid-length of the oesophagus, a pre-equatorial vulva, as well as a thin-walled and apparently underdeveloped rectum. Pairwise analyses based on ITS-28S and partial cox1 gene fragments showed significant differences between R. delangei n. sp. and its congeners from the Afrotropical Realm. Rhabdias delangei n. sp. is the 12th species of Rhabdias Stiles & Hassall, 1905 recorded in Afrotropical amphibians and the second species of the genus found in pyxicephalid hosts. Our phylogenetic analysis based on the ITS-28S region showed that the new species is closely related to the European species R. rubrovenosa (Schneider, 1866). Furthermore, both species are similar with respect to the underdeveloped rectum and pre-equatorial position of vulva.

Rhabdias glaurungi sp. nov. (Nematoda: Rhabdiasidae), parasite of Scinax gr. ruber (Laurenti, 1768) (Anura: Hylidae), from the Brazilian Amazon

The genus Rhabdias Stiles & Hassal, 1905 includes about 83 species of nematodes parasitic in amphibians and reptiles worldwide. Herein, we describe Rhabdias glaurungi sp. nov. from the hylid frog Scinax gr. ruber (Laurenti, 1768) in the Gunma Ecological Park, Santa Bárbara municipality, state of Pará, Brazil. This species has six small lips, an inflated cuticle along the entire body and a cup-shaped buccal capsule with smooth internal surface of its anterior part and irregularly folded internal surface of its posterior part in apical view. From the 17 valid species recognized in the Neotropical realm, the new species can be distinguished by the number of lips, the morphology and size of its buccal capsule, as well as the extent and shape of its cuticular inflation; in addition, there are molecular differences. Sequences of the mitochondrial Cytochrome c Oxidase subunit I gene strongly support the status of this form as a separate species. Molecular phylogenetic analysis shows R. glaurungi sp. nov. nested within the R. pseudosphaerocephala Kuzmin, Tkach & Brooks, 2007 species complex. Rhabdias glaurungi sp. nov. is the second species of the genus described from hosts of the family Hylidae in the Neotropical realm. We conclude that the diversity of Rhabdias within the Neotropics is likely largely underestimated.

First record of viviparity in polystomatid flatworms (Monogenea: Polystomatidae) with the description of two new species of Madapolystoma from the Madagascan anuran hosts Blommersia domerguei and Mantella expectata

Two frog species, Blommersia domerguei and Mantella expectata, are reported as hosts for new species of Madapolystoma. Phylogenetic analyses and genetic divergences observed in the genus supported the distinction of two morphotypes infesting selectively each host species and morphological investigation combining marginal hooklet morphometrics, genital spine number and measurements further showed that polystomes from the two host species differed from each other and from all other known polystomes. Madapolystoma magnahami n. sp. and Madapolystoma isaloensis n. sp. are therefore described as two new species. Advanced in utero development was illustrated in both polystome species following the observation of well developed hamuli and two pairs of haptoral suckers in developing embryos. Inside some of these in utero embryos a F2 generation embryo was also observed. This is the first report of true viviparity among polystomatid flatworms.

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Two new species of polystomes (Monogenetic flatworms) from Madagascar.

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First indication of true viviparity among the Polystomatidae.

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Unique life cycle with advanced degree of parental care.

Rhabdias bufonis (Rhabdiasidae) from the lung of the African common toad, Amietophrynus regularis (Bufonidae) in Egypt: new data on the basis of light and scanning electron microscopic study

Background and Aims

Rhabdias sp. (Rhabdiasidae) is a nematode parasite of family Rhabdiasidae infecting the lung of amphibians. The present study provides new morphological details for Rhabdias bufonis isolated from the lungs of the African common toad, Amietophrynus regularis based on observations of light and scanning electron microscopy (SEM).

Methods

Forty specimens were collected from its natural habitat: the damp, moist fields and gardens at Giza governorate, Egypt. Worms were isolated from the lungs, fixed and then preserved. They were examined using light and SEM with further line drawings.

Results

Fourteen specimens (35%) were found to harbor Rhabdias with an intensity of three to five worms per host. Bodies of the gravid females were elongated, slender, measured 3.22–9.86 (5.64 ± 0.03) long and 0.09–0.48 (0.23 ± 0.02) wide at mid-length. Buccal capsule was with cylindrical lumen and sclerotized walls. Ovaries were almost straight. The uteri were located anterior and posterior to the vulva. Uterus were filled with a large number of eggs (17–42). Eggs were oval in shape and some of them were with fully developed larvae inside. The tail was comparatively short, gradually tapered. SEM showed that worms possessed an oval anterior end with a simple, slit like oral opening. The lipless edges of the mouth opening were bordered with tiny cuticular elevations, radiated outwards. Two pairs of submedian cephalic papillae were observed around the oral opening as well as two amphids.

Conclusion

The current study presents new morphological details for R. bufonis isolated from the African common toad. Also, the morphology of the slit-like mouth opening, the two pairs of cephalic papillae, two amphids and the three pairs of cuticular elevations supporting the area around mouth opening were investigated.

Molecular and morphological characterisation of Rhabdias picardiae Junker, Lhermitte-Vallarino et Bain, 2010 (Nematoda: Rhabdiasidae) from Delaland's River Frog, Amietia delalandii (Duméril et Bibron, 1841) (Amphibia: Pyxicephalidae) in South Africa

Rhabdias picardiae previously known from the Guttural Toad, Sclerophrys gutturalis (Bufonidae) is described from a new host, Delaland's River Frog, Amietia delalandii (Pyxicephalidae). The species identification is confirmed by analysis of the COI gene sequence and morphological comparison with the original description. Morphological details of apical structures in adult parasitic R. picardiae, namely, the shape and position of lips, the number and position of external labial papillae, and the buccal capsule morphology are described using light and scanning electron microscopy. The buccal capsule width and length, the distance from anterior end to nerve ring and excretory pore, and ratios of distance to vulva to body length and body length to width were identified as less variable metrical characters in the studied sample of 30 specimens. Adult specimens demonstrated differences in the position of lips in relation to the oral opening and position of the buccal capsule in relation to the oesophagus depending on the size (age) of worms. The infective larvae of R. picardiae are described for the first time and characterised by two lateral alae consisting of two ridges, triangular pseudolabia with rounded tops, and presence of ornamentation on the rounded tail tip.

The morphology of free-living stages and immature parasites of Rhabdias paraensis (Nematoda: Rhabdiasidae), a parasite of Rhinella marina (Anura: Bufonidae) in Brazil

Rhabdias paraensis Santos, Melo, Nascimento, Nascimento, Giese et Furtado, 2011 was described based on fully gravid worms. Further investigations on the free-living stages, immature worms and young individuals were facilitated by cultivation in the laboratory, which allowed us to add new information about the morphology and development of the species. Observations on the free-living development of R. paraensis showed that the life cycle is typical of Rhabdias, with alternation of gonochoristic and hermaphroditic generations and without homogony. Males of the free-living generation were different from those in several species of the genus studied previously. In the original description, the excretory glands and duct were absent in gravid specimens of R. paraensis, while in this study, distinct excretory glands and a duct were observed in immature and young individuals. Additionally, we recognised the separation of the buccal capsule walls into anterior and posterior portions and described the specific shapes of these portions in lateral and apical view. Studies on the morphology and development of free-living stages of Rhabdias spp. from Neotropical regions may provide additional information for species determination.

A new species of Rhabdias Stiles et Hassall, 1905 (Nematoda: Rhabdiasidae) from Blommersia domerguei (Guibé) (Amphibia: Mantellidae) in Madagascar

Rhabdias blommersiae sp. n. (Nematoda: Rhabdiasidae) is described from the lungs of Domergue's Madagascar frog, Blommersia domerguei (Guibé) (Amphibia: Mantellidae), in Madagascar. The new species differs from congeners parasitizing amphibians in having a smaller body and buccal capsule, six equal lips, large excretory glands of unequal length and a posteriorly inflated body vesicle. A combination of characters distinguishes it from Afromalagasy species of Rhabdias Stiles et Hassall, 1905. Rhabdias blommersiae is the third species of the genus described from amphibians in Madagascar. Close similarities in the number and shape of circumoral structures in two Rhabdias species described from mantellid hosts in Madagascar suggest a close relationship and common origin of the two species, with subsequent adaptation to separate hosts within the Mantellidae.

Phylogenetic affinities and systematic position of Entomelas sylvestris Baker, 1982 (Nematoda: Rhabdiasidae), a parasite of Breviceps sylvestris FitzSimons (Amphibia: Brevicipitidae) in South Africa

The genus Entomelas Travassos, 1930 currently includes nine species of rhabdiasid nematodes, eight of them parasitic in lizards and only one, Entomelas sylvestris Baker, 1982, parasitic in amphibians. Entomelas sylvestris was originally described from the Forest Rain Frog Breviceps sylvestris FitzSimons in South Africa and was not reported since. It was placed in the genus Entomelas without any specific arguments for this taxonomic decision, presumably mainly based on details of the buccal capsule morphology. We have found this species in the same host in Limpopo province, South Africa. Molecular phylogenetic analysis based on the newly-obtained sequence of complete ITS region and partial nuclear large ribosomal subunit (28S) gene of E. sylvestris and previously published sequences of a variety of other rhabdiasid taxa, has convincingly demonstrated that this species does not belong in Entomelas. Instead, it clustered together with the members of Rhabdias Stiles & Hassall, 1905 from amphibian hosts. Therefore, we transfer E. sylvestris into Rhabdias as Rhabdias sylvestris (Baker, 1982) n. comb. In our analysis E. sylvestris appears, albeit with weak support, as a basal/sister taxon to the rest of Rhabdias spp. which explains to some extent the differences in the buccal capsule morphology between this species and other Rhabdias spp.

Molecular insight into systematics, host associations, life cycles and geographic distribution of the nematode family Rhabdiasidae

Rhabdiasidae Railliet, 1915 is a globally distributed group of up to 100 known species of nematodes parasitic in amphibians and reptiles. This work presents the results of a molecular phylogenetic analysis of 36 species of Rhabdiasidae from reptiles and amphibians from six continents. New DNA sequences encompassing partial 18S rDNA, ITS1, 5.8S rDNA, ITS2 and partial 28S rDNA regions of nuclear ribosomal DNA were obtained from 27 species and pre-existing sequences for nine species were incorporated. The broad taxonomic, host and geographical coverage of the specimens allowed us to address long-standing questions in rhabdiasid systematics, evolution, geographic distribution, and patterns of host association. Our analysis demonstrated that rhabdiasids parasitic in snakes are an independent genus sister to the rest of the Rhabdiasidae, a status supported by life cycle data. Based on the combined evidence of molecular phylogeny, morphology and life cycle characteristics, a new genus Serpentirhabdias gen. nov. with the type species Serpentirhabdias elaphe (Sharpilo, 1976) comb. nov. is established. The phylogeny supports the monophyly of Entomelas Travassos, 1930, Pneumonema Johnston, 1916 and the largest genus of the family, Rhabdias Stiles and Hassall, 1905. DNA sequence comparisons demonstrate the presence of more than one species in the previously monotypic Pneumonema from Australian scincid lizards. The distribution of some morphological characters in the genus Rhabdias shows little consistency within the phylogenetic tree topology, in particular the apical structures widely used in rhabdiasid systematics. Our data suggest that some of the characters, while valuable for species differentiation, are not appropriate for differentiation among higher taxa and are of limited phylogenetic utility. Rhabdias is the only genus with a cosmopolitan distribution, but some of the lineages within Rhabdias are distributed on a single continent or a group of adjacent zoogeographical regions. Serpentirhabdias, Entomelas and Pneumonema show rather strict specificity to their host groups. The evolution of the Rhabdiasidae clearly included multiple host switching events among different orders and families of amphibians as well as switching between amphibians and squamatan reptiles. Only a few smaller lineages of Rhabdias demonstrate relatively strict associations with a certain group of hosts.

Molecular evidence that Langeronia macrocirra and Langeronia cf. parva (Trematoda: Pleurogenidae) parasites of anurans from Mexico are conspecific

The genus Langeronia parasitizing the intestine of several species of anurans is distributed from North to Central America. We identified Langeronia macrocirra and Langeronia cf. parva from the same host and localities, and present here new data not applicable about their tegumental surface by scanning electron microscopy. We compared sequences of the rDNA ITS2 region and mtDNA cox1 gene for the two morphotypes. ITS2 exhibited a high degree of conservation. Phylogenetic reconstruction using cox1 revealed three clades (I, II, and III), which did not correspond to a previous identification or host. Little divergence was found within clades: sequences were identical in clade I, whereas clade II had 0.27% and clade III had 1.08%. Inter-clade divergence reached 8.69% (I vs. III). This pattern of genetic divergence indicated that both taxa probably belong to the same species, so we posit that the morphological changes could be correlated with development. Increasing sample size and geographical coverage will contribute to the taxonomy of the genus based on morphological and molecular evidence, and will open tracks toward the use of DNA barcodes to the genus in Mexico.

Rhabdias lacertae n. sp. (Nematoda: Rhabdiasidae), the first rhabdiasid species parasitising lizards in Europe

A new nematode species, Rhabdias lacertae n. sp. (Rhabdiasidae), is described from the body-cavity of the common lizard Lacerta vivipara Jacquin (Lacertidae) from the Ridge of Malá Fatra (Sokolie Hill), north-western Slovakia. The new species differs from its congeners mainly in possessing 3 min cuticular spikes at the tail tip and some other features. This is the first species of Rhabdias Stiles & Hassall, 1905 described from lizards in Europe and the first species of this genus parasitising hosts belonging to the Lacertidae.