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

Serpentirhabdias mexicanus n. sp. (Nematoda: Rhabdiasidae), a parasitic lungworm of the nauyaca viper Bothrops asper (Serpentes: Viperidae) in the Mexican Neotropics

Serpentirhabdias mexicanus n. sp. (Nematoda: Rhabdiasidae) is described from the lung of the nauyaca viper Bothrops asper in Puebla State, central Mexico. This new species is the fifth of the genus described having onchia. Among the species included in this group, the new species is morphologically closest to S. viperidicus and S. atroxi. However, it differs from both species mainly by having only one excretory gland (compared to two present in S. viperidicus and S. atroxi). In addition, S. mexicanus n. sp. can be separated of S. viperidicus by tail length, shape of vulval lips, geographic distribution and host species and from S. atroxi by body length, number of papillae in the cephalic region, as well as the host species and geographic distribution. In the present study, we propose the new species based on morphological, host spectrum and genetic evidence. Phylogenetic analysis indicated Serpentirhabdias as a monophyletic group, with two subgroups that are congruent with the presence/absence of onchia in the esophagostome, host association and other relevant morphological characters.

Cosmocerca goroensis n. sp. (Nematoda: Cosmocercidae) from South Africa and its phylogenetic relationships with other cosmocercids based on partial 28S sequences

Nematodes of the genus Cosmocerca are commonly found in various amphibians in South Africa and in most cases are identified as C. ornata. However, after detailed morphological studies and molecular approaches, three new species of the genus were recently described from three different frogs in South Africa. In present study, we describe another new species - Cosmocerca goroensis parasitising the Northern Pygmy Toad Poyntonophrynus fenoulheti in Soutpansberg mountains, Limpopo province, South Africa. The new species is characterised by prominent sex dimorphism, wide lateral alae, numerous somatic papillae in both sexes, and wide triangularly shaped gubernaculum and simple prominent spicules in males. Cosmocerca goroensis n. sp. distinguished from congeners, previously reported in Southern Africa by the shape of the gubernaculum and arrangement of somatic papillae in males. Morphological differences were confirmed by molecular analysis based on fragments of the 28S gene. Phylogenetic analysis based on the 28S gene fragments, including C. goroensis n. sp. and newly obtained sequence of C. ornata from Pelophylax lessonae from Ukraine, supported previously known data of closer relationships between species of Cosmocerca and Aplectana and more distant with Cosmocercoides spp.

Integrative taxonomy in the genus Rhabdias Stiles et Hassall, 1905 from anuran in Brazil, description of two new species and phylogenetic analyses

About 20 valid species of the genus Rhabdias are known in the Neotropical region. The present study aimed to describe two new species of Rhabdias parasitizing the lungs of Leptodactylus macrosternum and Leptodactylus podicipinus from Brazil. Distinctive characteristics between these species are numerous and based on body size, size of the buccal capsule, shape and size of the oesophagus, and position of the vulva. Molecular data based on ribosomal genes 28S and ITS region and mitochondrial COI of the two species are presented. Molecular analysis and comparison of the partial mitochondrial COI sequence of Rhabdias matogrossensis n. sp. and Rhabdias guaianensis n. sp. revealed a genetic divergence between these new species and the sequences of Rhabdias spp. previously deposited in GenBank. In the phylogenetic analysis, R. matogrossensis n. sp. was grouped with R. breviensis species complex, and R. guaianensis n. sp. was grouped as a sister group of R. cf. stenochepala. This study contributes to improving the diversity of known species of Rhabdias described in Brazilian anurans.

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.

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.

Three new species of Cosmocerca Diesing, 1861 (Nematoda: Cosmocercidae) parasitising frogs Cacosternum boettgeri Boulenger, 1882, Kassina senegalensis Dumeril and Bibron, 1841 and Phrynomantis bifasciatus Smith, 1847 from South Africa

Cosmocercid nematodes have been documented with much criticism due to the numerous inaccurate descriptions, redescriptions and synonymisation of found species. This is due to indistinguishable characters of females and the lack of male specimens found. Consequently, the species C. ornata is the most commonly found species worldwide and the only species of the genus reported in South Africa. In the present study, we found Cosmocerca in three different amphibian species, namely Cacosternum boettgeri, Kassina senegalensis and Phrynomantis bifasciatus. Based on differences in the shape of the gubernaculum and number of papillae, the found nematodes were assigned to three new species namely C. daly n. sp., C. monicae n. sp. and C. makhadoensis n. sp. Descriptions of species are followed by pairwise and phylogenetic analysis of partial ITS-28S sequences. All three species were found only in their host types from distant localities. Therefore, we hypothesise that host specificity of Cosmocerca from South African amphibians might be rather high and that the presence of C. ornata throughout South Africa is rather doubtful.

A new species of Rhabdias (Nematoda: Rhabdiasidae), a lung parasite of Pristimantis chiastonotus (Anura: Strabomantidae) from the Brazilian Amazon: description and phylogenetic analyses

Rhabdias Stiles and Hassal, 1905 comprises approximately 90 species of parasitic lung nematodes of amphibians and reptiles that have a wide distribution, with 21 species occurring in the Neotropics. In the present study, we describe Rhabdias waiapi n. sp. found parasitizing the lungs of the anuran species Pristimantis chiastonotus from the Amazon Biome in the Amapá State, Northern Brazil. The new species is characterized by having an elongated body, expansions of the cuticular inflation in the anterior end that become more discrete along the body, an anterior end with a slight constriction at the level of the esophageal apex with four rounded subapical elevations of the body wall, six lips, four near the edge of the oral opening and two more distant lateral ones, and a gradually tapering elongated tail. In addition, molecular analyses and phylogenetic reconstructions were made, with sequences from the coding region of the mitochondrial cytochrome c oxidase subunit I gene. Those results strongly support the status of the new taxon, which formed a poorly supported clade with Rhabdias sp. 5 from Anolis brasiliensis from Northeast Brazil. Rhabdias waiapi n. sp. is the 19th species of the genus described in the Neotropics for amphibians, the 10th in Brazil, the second described from hosts of the family Strabomantidae from the Neotropical region, and the first amphibian nematode species described in the Amapá State.

Insights into the phylogenetic position and phylogeography of the monospecific skink-parasite genus

Neoentomelas asatoi Hasegawa, 1989 is a parasitic nematode that infests only the scincid lizard Ateuchosaurus pellopleurus (Hallowell, 1861) that inhabits the forest floor in the Northern and Central Ryukyu Archipelago, Japan. As a member of Rhabdiasidae, the reproductive mode of N. asatoi is characterised by the alternation of the protandrous hermaphroditic mode and gonochoristic mode throughout the life cycle. The intrafamily phylogenetic position and intraspecific diversity of this nematode species were inferred by molecular phylogenetic analyses. The results revealed the phylogenetic distinctiveness of Neoentomelas Hasegawa, 1989 in Rhabdiasidae that supports the unique generic status of Neoentomelas within the family. The intraspecific phylogenetic analyses of N. asatoi revealed a minor concordant phylogenetic pattern with the host and mosaic geographic arrangement of the major clades that was discordant with the host. The analyses and distribution pattern of subclades suggested that this geographic arrangement can be explained by at least three dispersal events and subsequent switching to indigenous host populations. Colonisation events might be promoted by the high establishment rate of new populations stemming from the parthenogenesis-like reproduction mode of N. asatoi. This study demonstrated that reproductive modes can affect the intraspecific genetic diversity of parasites.

Spiroxys ankarafantsika Roca et Garcia, 2008 (Nematoda: Gnathostomatidae) and Other Nematodes Parasitising Pelusios spp. (Testudines: Pelomedusidae) from South Africa and Mozambique

INTRODUCTION

The nematode Spiroxys ankarafantsika was described parasitising freshwater turtles Pelusios castanoides and Pelomedusa subrufra from Madagascar. During parasitological surveys at different localities in Mozambique and South Africa the species was recovered from the digestive tract of Pelusios sinuatus, P. subniger and P. castanoides.

METHODS

The species were identified based on the morphology of the anterior extremity (absence of additional teeth on pseudolabia) and the male caudal end (number and arrangement of caudal papillae, size and shape of spicules). Molecular data included a 720 bp sequence fragment of 18S rDNA, the entire internal transcribed spacer 1 (ITS1), 5.8S rRNA, and internal transcribed spacer 2 (ITS), flanked by a 288 bp 18S rDNA sequence and about 1000 bp 28S rDNA sequence, and the mitochondrial cytochrome c oxidase subunit I (cox1) gene marker obtained in the present study.

RESULTS

All specimen recovered were identical, based on morphological and molecular data, with the exception of two specimens showing an intraspecific divergence of 9% based on a 694 bp sequence fragment of the cox1 gene. Additionally, a Contracaecum sp. third stage larva and an unidentified larva with mushroom-shaped anterior extremity were found. Descriptions of S. ankarafantsika and the two above-mentioned larval stages, supported by photomicrographs and molecular data 18S rDNA, ITS1-5.8S-ITS2-28S and cox1 gene fragments are presented herein.

A new species of Serpentirhabdias Tkach, Kuzmin et Snyder, 2014 (Nematoda: Rhabdiasidae) parasitic in the herald snake, Crotaphopeltis hotamboeia (Laurenti) (Reptilia: Serpentes: Colubridae) in South Africa

Serpentirhabdias mamlambo n. sp. is described from the lung of the herald snake, Crotaphopeltis hotamboeia (Laurenti) in KwaZulu-Natal Province, South Africa. The new species is characterised by the small lips, the absence of the buccal capsule, the large excretory glands (1.5-2.3 times longer than the oesophagus), and the numerous eggs in uteri. Serpentirhabdias mamlambo n. sp. differs from other Serpentirhabdias spp. in the presence of M-shaped cuticular folds on dorsal and ventral sides of apical surface, the eye-shaped internal labial papillae, and the distinct dilatation of the oesophagus at its mid-length. Morphological differentiation of S. mamlambo n. sp. from its congeners is supported by molecular evidence based on cox1 mitochondrial gene, and ITS and partial 28S region of nuclear rDNA. Serpentirhabdias mamlambo n. sp. is the first species of the genus Serpentirhabdias described from the Afrotropical Realm.

Do host habitat use and cospeciation matter in the evolution of Oswaldocruzia (Nematoda, Molineidae) from neotropical amphibians?

The genus Oswaldocruzia Travassos, 1917 includes approximately 90 species that are parasitic on amphibians and reptiles around the world, of which 43 occur in the neotropical region. However, molecular data supporting the taxonomic status of most species of the genus are scarce, and their phylogenetic relationships remain unknown. Using specimens of four molineid taxa (Oswaldocruzia belenensis Santos, Giese, Maldonado Jr. and Lanfredi, 2008; Oswaldocruzia chabaudi Ben Slimane & Durette-Desset, 1996, Oswaldocruzia chambrieri Ben Slimane & Durette-Desset, 1996 and Kentropyxia hylae Feitosa, Furtado, Santos and Melo, 2015) from amphibian hosts collected in different regions of Pará, Brazil, we conducted morphological studies, molecular analyses and phylogenies (maximum likelihood and Bayesian inference) using the cytochrome c oxidase subunity I (Cox1) gene. The newly generated sequences were compared with those of ten publicly available Cox1 sequences of Oswaldocruzia from Mexico. Our findings demonstrated significant differences between the sequences of amazonian specimens and sequences from specimens collected in Mexico, and we suggest that host-parasite cospeciation or habitat use might be related to molineid evolution in amphibian hosts. Additionally, this work presents new hosts and new geographical records for species of Oswaldocruzia from the neotropics.

Helminth fauna of Norops fuscoauratus (D'Orbigny, 1837) (Squamata: Dactyloidae) in the Atlantic Forest, northeastern Brazil

The composition of macro endoparasites associated with the lizard Norops fuscoauratus (Squamata) was analysed in two localities in the Atlantic Forest on the northeast of Brazil between December 2012 and July 2015. 74 specimens of N. fuscoauratus were examined and five species of helminths were reported, being: (a) for the population of Pernambuco: Cystacanth (Prevalence=37.5%), Physaloptera retusa Rudolphi, 1819 (Prevalence=4.16%), larva of flatworm (Prevalence=2.08%), Rhabdias sp. (Prevalence=2.08%) and Strongyluris oscari Travassos, 1923 (Prevalence=2.08%), and (b) of Alagoas: S. oscari (Prevalence=17.85%) and Rhabdias sp. (Prevalence=3.57%). The differences in the composition of endoparasites in the two populations are attributed to individualities of environments occupied by the lizards. The collection period does not influence the abundance of parasites, but when associated with sex, there was a positive correlation with the abundance of helminths, with more females than males being infected with parasites in the rainy season.

New records of Amphibiophilus spp. (Nematoda: Amphibiophilidae) parasitic in Strongylopus grayii (Smith) and Amietia delalandii (Duméril & Bibron) (Amphibia: Anura: Pyxicephalidae) in South Africa, with a description of Amphibiophilus bialatus n. sp

Nematodes of the genus Amphibiophilus Skrjabin, 1916 are a small group of parasites restricted to pyxicephalid frogs in southern Africa. In the present study, the new species A. bialatus parasitising the clicking stream frog Strongylopus grayii (Smith) as well as two forms parasitising the common river frog Amietia delalandii (Duméril & Bibron) from two distant localities are described. Amphibiophilus bialatus n. sp. clearly differs from the remaining species of the genus by having wide cervical alae, the dorsal oesophageal tooth not reaching the oral opening, and the presence of extra processes on the spicules. Specimens parasitising Am. delalandii in Mpumalanga Province and Limpopo Province, South Africa, differed from other species and from each other in the shape of the gubernaculum, though were almost identical in other characters. Based on morphological and molecular data, specimens from two localities were assigned to Amphibiophilus sp. 1 and Amphibiophilus sp. 2. Pairwise analyses of ITS-28S and cox1 gene fragments are presented for four Amphibiophilus spp.

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.

A two-step morphology-PCR strategy for the identification of nematode larvae recovered from muscles after artificial digestion at meat inspection

To ensure that meat from livestock and game is safe for human consumption, European legislation lays down rules for mandatory testing. Helminth larvae are a category of zoonotic foodborne pathogens that can contaminate meat. Among helminths, the only zoonotic nematode regulated in Europe regarding meat inspection is Trichinella spp.. It is precisely during Trichinella testing that other potentially zoonotic larvae can be found. Due to current lack of tools, their identification is often very complicated. Nematode larvae other than Trichinella, recovered from artificial digestions of pig and wild boar muscles from France and Germany, were subjected to a newly developed two-step identification scheme, which includes both morphological examination and molecular assays. The first step is a general orientation towards a broad taxonomic group; the second step consists of targeted identification based on the results of first step. Different parasites were identified, some of which were not zoonotic such as Metastrongylus spp. and Angiostrongylus vasorum, but others are known to be zoonotic such as Toxocara cati, Ascaris suum, and Uncinaria stenocephala. The strategy is efficient for the identification of nematode larvae recovered from muscles but could also be applied for larvae from other sources.

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.

Description, molecular characterization and life cycle of Serpentirhabdias mussuranae n. sp. (Nematoda: Rhabdiasidae) from Clelia clelia (Reptilia: Colubroidea) in Brazil

Serpentirhabdias mussuranae n. sp. is described from the lungs of the mussurana, Clelia clelia (Daudin, 1803), from vicinities of Lábrea, Amazonas State, Brazil. The species is characterized by the triangular oral opening, the presence of teeth (onchia) in the oesophastome, the excretory glands longer than the oesophagus and the tail abruptly narrowing in its anterior half and gradually tapering in posterior half. Among the Neotropical representatives of the genus, three species are known to possess the onchia in the oesophastome: S. atroxi, S. moi and S. viperidicus. Serpentirhabdias mussuranae n. sp. differs from S. atroxi and S. viperidicus by its triangular shape of the oral opening and the oesophastome in apical view, vs. round in the latter two congeners. Additionally, S. viperidicus has a larger oesophastome, 13-22 micrometers wide and 13-23 micrometers deep. The new species has relatively longer excretory glands than S. moi. The new species is morphologically and genetically close to S. atroxi, S. moi and S. viperidicus, all parasitic in Brazilian snakes, based on the presence of onchia and the comparison of nucleotide sequences of nuclear ribosomal DNA and mitochondrial cox1 gene (differences varied between 3.8% and 7.1%). Data on the life cycle of S. mussuranae n. sp. is provided, and the life cycle is typical of the genus Serpentirhabdias, with the combination of direct development and heterogony. Free-living larval stages and the adults of amphimictic free-living generation are described. The results of molecular phylogenetic analysis based on nuclear ribosomal internal transcribed spacer (ITS) + partial 28S region and partial mitochondrial cox1 gene are provided.

Helminth Community Dynamics in a Population of Pseudopaludicola Pocoto (Leptodactylidae: Leiuperinae) from Northeast-Brazilian

Climatic variation in low latitudes influences the dynamics and structure of parasite communities. Environmental changes caused by dry and rainy seasons alter prevalence and abundance of endoparasite communities. In addition to providing a list of the helminth species associated with the swamp frog Pseudopaludicola pocoto, this study aimed to investigate the effects of rainfall and temperature on parasitological descriptors of helminths associated with P. pocoto in an area of the semiarid zone. A total of 817 swamp frog specimens were collected between 2013 and 2017, with four sampling expeditions during the dry season and four during the rainy season. Environmental parameters of temperature and rainfall were compared to the parasitological descriptors of prevalence, abundance and mean infection intensity of the parasite community using a multivariate linear regression. A richness of eight parasite species was identified, including Nematoda (Rhabdias sp., Cosmocerca parva, Oxyascaris oxyascaris, Physaloptera sp., Brevimulticaecum sp., Spiroxys sp. and unidentified nematode) and Acanthocephala (cystacanths). Rainfall levels had a significant effect on the infection intensity of Rhabdias sp. being the presence of this species higher during the rainy season, whereas no influence of temperature was observed on the helminth community.

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.

Description, biology and molecular characterisation of Serpentirhabdias moi n. sp. (Nematoda: Rhabdiasidae) from Chironius exoletus (Serpentes: Colubridae) in Brazil

A new species of the genus Serpentirhabdias Tkach, Kuzmin et Snyder, 2014, S. moi n. sp., is described from a colubroid snake Chironius exoletus from Caxiuanã National Forest, State of Pará, Brazil. The species is characterised by having a triangular oral opening, absence of the buccal capsule, presence of six minute onchia in the oesophastome, and excretory glands of approximately the same length as the oesophagus. These qualitative morphological characters, as well as some measurements, differentiate the new species from other Neotropical and Nearctic Serpentirhabdias spp. The morphological description of parasitic adults of S. moi n. sp. is complemented by the description of free-living stages including males, females, and infective larvae. Comparative analysis of partial sequences of cox1 and 12S mitochondrial genes strongly supported the status of S. moi n. sp. as a new species. Molecular phylogeny based on sequences of the nuclear DNA region spanning the 3' end of the 18S nuclear rRNA gene, ITS region (ITS1 + 5.8S + ITS2) and 5' end of the 28S gene supported monophyly of all rhabdiasid genera included in the analysis and placed the new species into the Serpentirhabdias clade as sister taxon to S. fuscovenosa.

Allopatric speciation of Meteterakis (Heterakoidea: Heterakidae), a highly dispersible parasitic nematode, in the East Asian islands

To clarify how the species diversity of highly dispersible parasites has developed, molecular phylogenetic analyses of Meteterakis spp., multi-host endoparasitic nematodes of reptiles and amphibians from the East Asian islands, were conducted. The results demonstrated the existence of two major clades, the J- and A-groups, with exclusive geographic ranges that are discordant with the host faunal province. However, diversification within the J-group was concordant with the host biogeography and suggested co-divergence of this group with vicariance of the host fauna. In contrast, the phylogenetic pattern within the A-group was discordant with host biogeography and implied diversification by repeated colonization. In addition, the mosaic distribution pattern of a J-group and an A-group species in the Japanese Archipelago, along with comparison of population genetic parameters and the genetic distance from their closest relatives, suggested the initial occurrence of a J-group lineage followed by exclusion in the western part of this region caused by invasion of an A-group lineage. Thus, the present study suggested that the species diversity of highly dispersible parasites including Meteterakis is formed not only by co-divergence with host faunal vicariance but also by peripatric speciation and exclusive interactions between species.

Of poisons and parasites-the defensive role of tetrodotoxin against infections in newts

Classical research on animal toxicity has focused on the role of toxins in protection against predators, but recent studies suggest these same compounds can offer a powerful defense against parasites and infectious diseases. Newts in the genus Taricha are brightly coloured and contain the potent neurotoxin, tetrodotoxin (TTX), which is hypothesized to have evolved as a defense against vertebrate predators such as garter snakes. However, newt populations often vary dramatically in toxicity, which is only partially explained by predation pressure. The primary aim of this study was to evaluate the relationships between TTX concentration and infection by parasites. By systematically assessing micro- and macroparasite infections among 345 adult newts (sympatric populations of Taricha granulosa and T. torosa), we detected 18 unique taxa of helminths, fungi, viruses and protozoans. For both newt species, per-host concentrations of TTX, which varied from undetectable to >60 μg/cm² skin, negatively predicted overall parasite richness as well as the likelihood of infection by the chytrid fungus, Batrachochytrium dendrobatidis, and ranavirus. No such effect was found on infection load among infected hosts. Despite commonly occurring at the same wetlands, T. torosa supported higher parasite richness and average infection load than T. granulosa. Host body size and sex (females > males) tended to positively predict infection levels in both species. For hosts in which we quantified leucocyte profiles, total white blood cell count correlated positively with both parasite richness and total infection load. By coupling data on host toxicity and infection by a broad range of micro- and macroparasites, these results suggest that-alongside its effects on predators-tetrodotoxin may help protect newts against parasitic infections, highlighting the importance of integrative research on animal chemistry, immunological defenses and natural enemy ecology.

New information on morphology and molecular data of camallanid nematodes parasitising Xenopus laevis (Anura: Pipidae) in South Africa

Three species of nematodes from the Camallanidae that are known to infect Xenopus laevis Daudin (Anura: Pipidae) were collected from several localities across South Africa. New data on morphology, partial 28S and cox1 genes, infection levels and distribution are presented herein. The most common species, Batrachocamallanus slomei Southwell et Kirshner, 1937, from the stomach and less often oesophagus, was found in eight localities. Camallanus kaapstaadi Southwell et Kirshner, 1937, also from the oesophagus, was found in two localities and C. xenopodis Jackson et Tinsley, 1995, from the intestine, at a single locality. New localities for both C. kaapstaadi and C. xenopodis provide a geographical range extension. Males of C. xenopodis are described for the first time herein. The existence of a left spicule in the males of both the species of Camallanus Railliet and Henry, 1915 is confirmed and measurements are provided. Although C. xenopodis is distinguished from C. mazabukae Kung, 1948 in the present study, we suggest greater sampling effort in other African amphibians to confirm the species status of the latter taxon. Finally, the new molecular data showed distant relationships between collected species of Camallanus and species parasitising fish and freshwater turtles.

New records of Helminths in Reptiles from five states of Brazil

Forty five specimens representing nine species of reptile (Salvator merianae, Enyalius bilineatus, Amphisbaena alba, Xenopholis undulatus, Chironius fuscus, Helicops angulatus, Chironius flavolineatus, Erythrolamprus viridis and Crotalus durissus) collected in five Brazilian states were examined for helminths. Twelve helminth species were found as follow: nine Nematoda (Physaloptera tupinambae, Strongyluris oscari, Paracapillaria sp., Dracunculus brasiliensis, Physaloptera liophis, Serpentirhabias sp. 1, Serpentirhabias sp. 2, Serpentirhabias sp. 3 and Aplectana sp.), one Cestoda (Semenoviella amphisbaenia), one Trematoda (Paracotyletrema sp.), and one Acantocephala (Centrorhynchus sp.). Ten new host records and seven new locality records were reported.

Morphometric and phylogenetic analyses of Serpentirhabdias viperidicus n. sp. (Nematoda: Rhabdiasidae) from the lancehead snake Bothrops moojeni Hoge, 1966 (Reptilia: Serpentes: Viperidae) in Brazil

Serpentirhabdias viperidicus n. sp. (Nematoda: Rhabdiasidae) is described from the lungs of the ‘Brazilian lancehead’ Bothrops moojeni (Hoge, 1966) from the savannah in São Paulo State, Brazil. The new species is the eighth species of Serpentirhabdias described in the Neotropical region, and differs from other species mainly by a combination of characters: lips slightly notable, presence of fine striations at posterior ends, presence of two parallel lines with intercalated pores, a pore-shaped phasmid situated at the level of the anal aperture and another two in the posterior half of the tail. It is the first species of Serpentirhabdias reported in this snake host and the second species of this genus found parasitizing South American viperidian snakes. Molecular phylogenetic analysis using ribosomal (ITS and 28S partial) genes confirms Serpentirhabdias viperidicus n. sp. as a new species that clustered in the Serpentirhabdias clade, sister taxon to Serpentirhabdias fuscovenosa and Serpentirhabdias elaphe. This is the first description of Serpentirhabdias species from Brazil using molecular approaches and morphological characters to confirm the monophyly of this recent genus.

Phenotypic plasticity and developmental innovations in nematodes

Developmental plasticity has been implicated as a facilitator for phenotypic diversification, but the molecular mechanisms controlling it are largely unknown. We review recent comparative analyses in non-Caenorhabditis nematodes that display polyphenisms in larval development, mouth morphology and reproductive mode. Some of the challenges ahead will be to connect how these phenotypic traits are linked to each other at the molecular level, and at the ecological level. This will require sampling of several nematode species, the characterization of their ecology and the employment of both classical genetics and recently developed technological advances, such as genome editing.

Rhinella marina (Amphibia: Bufonidae) Versus Rhabdias paraensis (Nematoda: Rhabdiasidae): Expanding the View on a Natural Infection

Amphibian and reptile lungs are frequently infected with Rhabdias parasites, and this condition ultimately leads to reduced survival, performance, and growth because of granulomatous inflammation, nodule formation, and nematodal pneumonia onset. Here we investigate the histopathological features of naturally infected Rhinella marina by the lung nematode Rhabdias paraensis. A total of 10 host animals were captured in peridomiciliar areas in the eastern Brazilian Amazon, and anatomic-histological analyses were performed on both the infected and non-infected lungs of these amphibians. Helminths were usually found within the secondary and primary septa of infected lungs whereas parasites were not detected within vessels or adhering to tissues. In addition, we observed discrete erythrocytes, diapedesis foci, few granulocytes and erythrocytes in the interseptal spaces, discrete cell infiltration, and a small number of melanomacrophages, and no granulomas or cysts were observed. New aspects related to changes in tissue and helminth-host interactions are discussed for the relationship of R. paraensis × Rhi. marina from the Amazon region.

Description of Serpentirhabdias atroxi n. sp. (Nematoda: Rhabdiasidae), a parasite of Bothrops atrox (Linnaeus) (Reptilia: Serpentes: Viperidae) in Brazilian Amazonia

A new lung-dwelling nematode species is described from the common lancehead Bothrops atrox (Linnaeus) in the Brazilian Amazon Region. The species is assigned to the genus Serpentirhabdias Tkach, Kuzmin & Snyder, 2014 based on the presence of six lips arranged in two lateral groups, the absence of prominent cuticular inflations, and lung parasitism in snakes. Serpentirhabdias atroxi n. sp. differs from other species of the genus mainly by details of the morphology of the anterior end: cuticularised ring surrounding the anterior part of the buccal cavity and six minute onchia present in the oesophastome. Serpentirhabdias atroxi n. sp. is the seventh species of the genus known from the Neotropical Realm and the second species described from viperid snakes.

Mating dynamics in a nematode with three sexes and its evolutionary implications

Nematodes have diverse reproductive strategies, which make them ideal subjects for comparative studies to address how mating systems evolve. Here we present the sex ratios and mating dynamics of the free-living nematode Rhabditis sp. SB347, in which males, females and hermaphrodites co-exist. The three sexes are produced by both selfing and outcrossing, and females tend to appear early in a mother’s progeny. Males prefer mating with females over hermaphrodites, which our results suggest is related to the female-specific production of the sex pheromones ascr#1 and ascr#9. We discuss the parallels between this system and that of parasitic nematodes that exhibit alternation between uniparental and biparental reproduction.

Subspectacular nematodiasis caused by a novel Serpentirhabdias species in ball pythons (Python regius)

Subspectacular nematodiasis was diagnosed in three captive-bred juvenile ball pythons (Python regius) from two unrelated facilities within a 6-month period. The snakes were presented with similar lesions, including swelling of facial, periocular and oral tissues. Bilaterally, the subspectacular spaces were distended and filled with an opaque fluid, which contained nematodes and eggs. Histopathology showed nematodes throughout the periocular tissue, subspectacular space and subcutaneous tissue of the head. The nematodes from both facilities were morphologically indistinguishable and most closely resembled Serpentirhabdias species. Morphological characterization and genetic sequencing indicate this is a previously undescribed rhabdiasid nematode.

A new species of Serpentirhabdias Tkach, Kuzmin & Snyder, 2014 (Nematoda: Rhabdiasidae) parasitic in the brown ground snake Atractus major Boulenger (Reptilia: Serpentes: Dipsadidae) in Brazil

Serpentirhabdias atracti n. sp. is described based on specimens discovered in the lung of Atractus major Boulenger from Caxiuanã National Forest, Pará, Brazil. The new species is assigned to Serpentirhabdias Tkach, Kuzmin & Snyder, 2014 based on morphological characters (comparatively thin body cuticle without prominent inflations, arrangement of circumoral papillae in two lateral groups, pre-equatorial position of vulva, eggs in uteri at early cleavage stages), as well as because of its parasitism in snakes. The new species is most similar to S. vellardi (Pereira, 1928) due to the absence of lips and buccal capsule, similar body dimensions, and the specificity to dipsadid snakes in Brazil. The two species differ in the shape of the tail (bulbous dilatation in the posterior part followed by a thread-like tail tip present in S. atracti n. sp.), the width of the oesophagus, and the size of the excretory glands. Serpentirhabdias atracti n. sp. is the sixth species of this genus found in the Neotropical Region.

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.