Integrative approach on Pharyngodonidae (Nematoda: Oxyuroidea) parasitic in reptiles: Relationship among its genera, importance of their diagnostic features, and new data on Parapharyngodon bainae

MOLECULAR PHYLOGENETIC ANALYSIS OF GYRINICOLA BATRACHIENSIS (NEMATODA: OXYUROIDEA) LENDS SUPPORT TO THE MONOPHYLY OF THE GENUS AND THE RESURRECTION OF GYRINICOLINAE

Gyrinicola Yamaguti, 1938, includes 6 species of oxyurid found within the intestinal tract of numerous, larval, anuran species in Europe, Asia, South America, and North America. The systematic placement and hierarchical treatment of the genus has shifted at least 5 times since its discovery; the group was first considered as its own family (Gyrinicolidae), then treated as a subfamily (Gyrinicolinae) of Cosmocercidae, then as a member of the Pharyngodonidae, followed by movement back to the Cosmocercidae, and finally a recent proposal suggested the resurrection of the Gyrinicolidae. Species in the genus vary widely in the morphology of the uterine tract, a characteristic often used to indicate membership in the genus, as it is tied to the reproductive mode. However, until recently very few genetic data were available to aid in the placement of this unique group of worms, and before this study to the best of our knowledge none existed for the North American species. To examine the monophyly and placement of the Gyrinicola we sampled populations of Gyrinicola batrachiensis across North America and screened them for genetic diversity using nuclear markers 18S and 28S. Phylogenies suggest at least 3 clades exist among the nematodes from North America and that these clades, alongside Gyrinicola japonica, form a well-supported group within Oxyuroidea. Further representation of Pharyngodonidae from other vertebrate classes may help clarify the relationship of this historical grouping to other members of the Oxyuroidea.

A Phylogenetic Assessment of Nematodes (Oxyuroidea: Pharyngodonidae) Infecting Moroccan Lizards

Molecular tools can be used to estimate the phylogeny of species and to identify cryptic diversity, but their use for parasites has lagged behind that of free-ranging organisms. As an example, in North Africa there is minimal molecular data available for helminth parasites of lizards. In this work we used two molecular markers (the nuclear 18S rRNA and the mitochondrial Cytochrome c Oxidase subunit 1) to investigate the diversity of nematodes of the family Pharyngodonidae parasitizing three genera of lizards from Morocco (Chalcides, Quedenfeldtia and Tarentola) and to explore their co-evolutionary history. Morphological assessments indicated that members of three genera were present: Spauligodon, Thelandros, and Parapharyngodon. Phylogenetic analysis of 18S rRNA sequences indicated the monophyly of the genus Spauligodon, and that some lineages could be distinguished, including Spauligodon auziensis from the host species Tarentola mauritanica, and another unnamed lineage from hosts of the genus Chalcides. However, with this slow-evolving marker some species could not be distinguished. The genus Thelandros was not monophyletic, although relationships were not strongly supported. Analysis of the faster evolving mitochondrial marker clearly separated various species of Spauligodon, as well as distinct unnamed lineages identified in the host genus Chalcides and the host Quedenfeldtia moerens.

New species of Parapharyngodon (Nematoda: Pharyngodonidae) parasite of Osteocephalus taurinus (Anura: Hylidae) from Northern Brazilian Amazon Region

Parapharyngodon spp. are nematodes parasites of amphibian and reptiles worldwide distributed. Of 55 valid species, only 11 are known for the Neotropical realm, and six were found parasitizing hylid frogs in the world. In the present work, we describe a new species of Parapharyngodon from the large intestine of Osteocephalus taurinus from Reserva de Desenvolvimento Mamirauá, Amazonas, Brazil, using light and scanning electron microscopy. Parapharyngodon curupira n. sp. is allocated to the group of species with three pairs of cloacal papillae. However, it shows a set of different morphological characters compared to its congeners. In the new species, males have gubernaculum and smooth cloacal lip, females have pre-bulbar ovaries, and we also observed some morphometric differences. Among Parapharyngodon spp. from the Neotropical realm, the new taxon resembles P. alverangai and P. politoedi. The last species was described from the same host and biome (Amazon); however, they can be easily distinguished from new species by the presence of gubernaculum and v-shape structure at the lower caudal lip. Thus, we characterize and propose a new species of Parapharyngodon from the western amazon.

Deep in the systematics of Camallanidae (Nematoda): using integrative taxonomy to better understand the phylogeny and consistency of diagnostic traits

Due to conflicts between classic and molecular systematics of Camallanidae, different data types were used for the first time, to better understand the evolutionary history and taxa consistency within this family. Genetic [18S and 28S rDNA; cytochrome c oxidase subunit I (COI) mtDNA], morphological and life history traits were used to infer phylogenies using Bayesian inference, reconstructed from separated and concatenated datasets. The consistency of tree and morphological traits was evaluated using the consistency index. Characters were mapped on the trees and the phylogenetic informativeness of genetic markers was estimated. Phylogenetic informativeness of 18S provided better resolution for outer nodes, COI for inners and 28S had an intermediate profile. New sequences for two camallanid species were obtained. Phylogenies of genetic and concatenated data largely agreed, showing more divergence in the COI dataset, due to its higher mutation rate vs stable morphology for diagnosing higher taxa. No genus sustained monophyly. The lack of autapomorphy and phylogenetic proximity supported the partition of Batrachocamallanus as synonym of Procamallanus and Spirocamallanus, which should not be considered as subgenera. Although traits of buccal capsule, male tail, habitat, host and biogeographic were highly consistent, intrinsic patterns varied according to different taxa assemblages. Morphological systematics of Camallanidae, based on buccal capsule, is artificial for certain taxa.

Morphology, genetic characterization and molecular phylogeny of pinworm Skrjabinema longicaudatum n. sp. (Oxyurida: Oxyuridae) from the endangered Tibetan antelope Pantholops hodgsonii (Abel) (Artiodactyla: Bovidae)

Background

The Tibetan antelope Pantholops hodgsonii (Abel) (Artiodactyla: Bovidae) is an endangered species of mammal endemic to the Qinghai-Tibetan Plateau. Parasites and parasitic diseases are considered to be important threats in the conservation of the Tibetan antelope. However, our present knowledge of the composition of the parasites of the Tibetan antelope remains limited.

Methods

Large numbers of nematode parasites were collected from a dead Tibetan antelope. The morphology of these nematode specimens was observed using light and scanning electron microscopy. The nuclear and mitochondrial DNA sequences, i.e. small subunit ribosomal DNA (18S), large subunit ribosomal DNA (28S), internal transcribed spacer (ITS) and cytochrome c oxidase subunit 1 (cox1), were amplified and sequenced for molecular identification. Moreover, phylogenetic analyses were performed using maximum likelihood (ML) inference based on 28S and 18S + 28S + cox1 sequence data, respectively, in order to clarify the systematic status of these nematodes.

Results

Integrated morphological and genetic evidence reveals these nematode specimens to be a new species of pinworm Skrjabinema longicaudatum (Oxyurida: Oxyuridae). There was no intraspecific nucleotide variation between different individuals of S. longicaudatum n. sp. in the partial 18S, 28S, ITS and cox1 sequences. However, a high level of nucleotide divergence was revealed between the new species and its congeners in 28S (8.36%) and ITS (20.3–23.7%) regions, respectively. Molecular phylogenetic results suggest that the genus Skrjabinema should belong to the subfamily Oxyurinae (Oxyuroidea: Oxyuridae), instead of the subfamily Syphaciidae or Skrjabinemiinae in the traditional classification, as it formed a sister relationship to the genus Oxyuris.

Conclusions

A new species of pinworm Skrjabinema longicaudatum n. sp. (Oxyurida: Oxyuridae) is described. Skrjabinema longicaudatum n. sp. represents the first species of Oxyurida (pinworm) and the fourth nematode species reported from the Tibetan antelope. Our results contribute to the knowledge of the species diversity of parasites from the Tibetan antelope, and clarify the systematic position of the genus Skrjabinema.

Morphological description and phylogenetic assessment of 28S rRNA for Thelandros chalcidiae sp. nov. from Chalcides ocellatus

Thelandros is a genus of oxyurid nematodes which parasitize both omnivorous and herbivorous hosts. Thelandros chalcidiae sp. nov. is a new taxa described from the large intestine of the ocellated skink, Chalcides ocellatus, from the South Sinai Desert in Egypt. The recovered parasite species was examined at both morphological and molecular levels in order to determine the exact taxonomic position within Pharyngodonidae family. The current pharyngodonid species is characterized by a mouth opening bounded by three bilobed lips; male worms are characterized by the presence of two pairs of cloacal papillae (pre- and adcloacal) and one single caudal papillae (postcloacal) and caudal alae in an auricular form and females with post-equatorial vulva, amphidelphic ovary in which anterior ovary extended to level of excretory pore and posterior ovary extended posteriorly up anal opening. The recovered nematodes were compared with other known species from different hosts and it was found to be morphologically different from them. Molecular characterization based on the partial 28S rRNA nuclear ribosomal gene sequence showed sequence identities ≥ 83.15% with taxa under family Pharyngodonidae, 74.84-87.37% with Oxyuridae, 80.54% with Heteroxynematidae, and 75.98-77.72% with Thelastomatidea. Phylogenetic analysis showed that parasite sequence in conjunction with existing data facilitate placement of this species within Oxyurida. The present species is deeply embedded in genus Thelandros with close relationships to previously described Thelandros sp. and T. galloti in same taxon. This study highlighted importance of combining morphological and genetic data with taxonomy in pharyngodonid species.

Redescription of Gyrinicola japonica, a Tadpole-Endoparasitic Nematode from Japan, with Resurrection of the Family Gyrinicolidae (Nematoda: Oxyurina)

The taxonomic account of the tadpole-parasitic nematode Gyrinicola japonica Yamaguti, 1938, which is the type species of the genus, was reassessed based on syntypes and newly-collected specimens from the type locality. Our redescription of G. japonica addresses the erroneous original description of a spicule in this nematode, and emends the diagnosis of the species. Additionally, molecular phylogenetic trees based on nuclear 18S and 28S rDNA sequences revealed that G. japonica forms a distinctive lineage within the suborder Oxyurina, and this tadpole-specialist is phylogenetically close to the lizard-parasitic nematodes that belong to the family Pharyngodonidae. The results of morphological examination with the aid of molecular phylogenetic trees highlight the systematic uniqueness of this tadpole-parasitic group within Oxyurina, and Gyrinicolidae is accordingly resurrected as a distinctive oxyurinan family, with redefinition of the family and the genus Gyrinicola.