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Carnoya mexicana n. sp. Female: A-D, F. A: Habitus; B: Anterior region, ventral view; C: Anterior region, stoma, lateral view; D: Anterior region, oesophagus, ventral view; F: Vulva, left lateral view. Male: E, G, H, I. E: Habitus; G: Cloacal region, ventral view; H: Stoma and anterior pharynx, ventral view; I: Spicule and gubernaculum right lateral view. (Scale bars = 50 μm.)
Source publication
Carnoya cepacapitatus n. sp. and C. mexicana n. sp. from the intestine of Anadenobolus putealis from Mexico are described herein. Specific characters like the number of collars and spines set these species apart from those previously described from the Caribbean and South American regions. Males of C. cepacapitatus n. sp. can be differentiated from...
Citations
... Rhigonematomorph nematodes belonging to Carnoya, Heth and Ransomnema were collected in 2013 and 2014 from five females of Anadenobolus putealis Loomis, an endemic epigean spiroboloid from two distinct areas within the boundaries of the Biosphere Reserve of Los Tuxtlas in the State of Veracruz, Mexico (Loomis, 1969;Bueno-Villegas, 2003;Mejía-Madrid, 2014, 2015. Fur-ther nematode sampling included an undescribed species of Heth found in an unidentified spirobolid (Atopetholidae Chamberlin) from Oaxaca. ...
A molecular hypothesis of the Infraorder Rhigonematomorpha is presented. The phylogeny recovered using combined SSU and LSU markers suggests that the Rhigonematomorpha is nested within a larger clade that includes Ascaridomorpha, Spiruromorpha and Oxyuridomorpha and is strongly supported by maximum likelihood (ML) bootstrap support values (BS) and Bayesian posterior probabilities (BPP). SSU and LSU ML and Bayesian analyses recovered Rhigonematomorpha as a paraphyletic clade. In the ML and Bayesian analyses of a combined matrix of complete to partial sequences of SSU and LSU, respectively, Rhigonematomorpha is recovered as a monophyletic clade with moderate BPP but low BS. Highly supported BS and BPP of a combined SSU and LSU matrix support a hypothesis of a monophyletic Superfamily Ransomnematoidea that includes the families Carnoyidae, Hethidae, Ransomnematidae plus a Brumptaemilius, Cattiena, Insulanema clade, and a monophyletic Superfamily Rhigonematoidea that probably includes the paraphyletic families Rhigonematidae and Ichthyocephalidae. It is suggested that the future inclusion of more families and genera might help resolve the monophyly of the Infraorder Rhigonematomorpha as advanced here.
Background
The infraorder Rhigonematomorpha comprises a group of obligate parasitic nematodes of millipedes (Arthropoda: Diplopoda). The current species identification of Rhigonematomorpha nematodes remains mainly based on morphological features, with molecular-based identification still in its infancy. Also, current knowledge of the phylogeny of Rhigonematomorpha is far from comprehensive.
Methods
The morphology of Rhigonematomorpha nematodes belonging to the genus Rhigonema , collected from the millipede Spirobolus bungii Brandt (Diplopoda: Spirobolida) in China, was studied in detail using light and scanning electron microscopy. Five different genetic markers, including the nuclear small ribosomal subunit (18S), internal transcribed spacer (ITS) and large ribosomal subunit (28S) regions and the mitochondrial cox 1 and cox 2 genes of these Rhigonematomorpha nematodes collected from China and Rhigonema naylae collected from Japan were sequenced and analyzed using Bayesian inference (BI) and Assemble Species by Automatic Partitioning (ASAP) methods. Phylogenetic analyses that included the most comprehensive taxa sampling of Rhigonematomorpha to date were also performed based on the 18S + 28S genes using maximum likelihood (ML) and BI methods.
Results
The specimens of Rhigonema collected from S. bungii in China were identified as a new species, Rhigonema sinense n. sp. Striking variability in tail morphology was observed among individuals of R. sinense n. sp. ASAP analyses based on the 28S, ITS, cox 1 and cox 2 sequences supported the species partition of R. sinense n. sp. and R. naylae , but showed no evidence that the different morphotypes of R. sinense n. sp. represent distinct genetic lineages. BI analyses also indicated that R. sinense n. sp. represents a separated species from R. naylae based on the cox 1 and cox 2 genes, but showed that R. naylae nested in samples of R. sinense n. sp. based on the ITS and 28S data. Phylogenetic results showed that the representatives of Rhigonematomorpha formed two large clades. The monophyly of the families Carnoyidae and Ichthyocephalidae and the genus Rhigonema was rejected. The representatives of the family Ransomnematidae clustered together with the family Hethidae with strong support.
Conclusions
A new species of Rhigonematomorpha, R. sinense n. sp. is described based on morphological and molecular evidence. ASAP analyses using 28S, ITS, cox 1 and cox 2 data indicate the striking variability in tail morphology of R. sinense n. sp. as intraspecific variation, and also suggest that partial 28S, ITS, cox 1 and cox 2 markers are effective for molecular identification of Rhigonematomorpha nematodes. The phylogenetic results support the traditional classification of Rhigonematomorpha into the two superfamilies Rhigonematoidea and Ransomnematoidea, and indicate that the families Carnoyidae and Ichthyocephalidae and the genus Rhigonema are non-monophyletic. The present phylogeny strongly supports resurrection of the family Brumptaemiliidae, and also indicates that the family Ransomnematidae is sister to the family Hethidae.
Graphical Abstract
Ransomnema bravoae from the intestine of the endemic rhinocricid, Anadenobolus putealis , from Mexico, is redescribed. This species was originally described from the spirobolid Hiltonius carpinus from Morelos State, Mexico. A redescription is presented and a neotype proposed due to the loss of the type material. Ransomnema bravoae can be distinguished from all other described species of Ransomnema by the presence of a cervical expansion extending from the base of the buccal cone to approximately the last one-third of the muscular pharynx and is offset by a slight constriction at the termination point, the presence of broad lateral alae beginning at the cervical expansion termination and terminating at the phasmids, the size and distribution of the male caudal papillae, and the size of the spicules, the right spicule being 3-4 times longer than the left. Ransomnema bravoae resembles R. alatum and R. bursatum in the presence of lateral alae but differs markedly in their distribution along the body. The right spicule is within the size range of that of R. longispiculum . Males of R. bravoae possess the usual papillal composition of the genus and are very similar to that of R. christiei in that the last pair of papillae is arranged in tandem. It is similar to species where males possess three precloacal papillae placed on lateral protuberances, showing morphological affinities to Caribbean species R. artigasi and R. habanense from Cuba.
