Topic
Trichocephalida
About: Trichocephalida is a research topic. Over the lifetime, 2 publications have been published within this topic receiving 14 citations.
Papers
TL;DR: A survey of the nature and phylogenetic distribution of nematode vulval appendages revealed 3 major classes based on composition, position, and orientation that included membranes, flaps, and epiptygmata.
Abstract: A survey of the nature and phylogenetic distribution of nematode vulval appendages revealed 3 major classes based on composition, position, and orientation that included membranes, flaps, and epiptygmata. Minor classes included cuticular inflations, protruding vulvar appendages of extruded gonadal tissues, vulval ridges, and peri-vulval pits. Vulval membranes were found in Mermithida, Triplonchida, Chromadorida, Rhabditidae, Panagrolaimidae, Tylenchida, and Trichostrongylidae. Vulval flaps were found in Desmodoroidea, Mermithida, Oxyuroidea, Tylenchida, Rhabditida, and Trichostrongyloidea. Epiptygmata were present within Aphelenchida, Tylenchida, Rhabditida, including the diverged Steinernematidae, and Enoplida. Within the Rhabditida, vulval ridges occurred in Cervidellus, peri-vulval pits in Strongyloides, cuticular inflations in Trichostrongylidae, and vulval cuticular sacs in Myolaimus and Deleyia. Vulval membranes have been confused with persistent copulatory sacs deposited by males, and some putative appendages may be artifactual. Vulval appendages occurred almost exclusively in commensal or parasitic nematode taxa. Appendages were discussed based on their relative taxonomic reliability, ecological associations, and distribution in the context of recent 18S ribosomal DNA molecular phylogenetic trees for the nematodes. Characters were found to be distributed across subsets of terminal and phylogenetically distant taxa, demonstrating considerable homoplasy. Accurate definitions, terminology, and documentation of the taxonomic distribution of vulval appendages are important in evaluations of hypotheses for either
15 citations
TL;DR: In this paper, the evolutionary relationship of the Fatty acid and retinol-binding proteins (FARs) across the phylum Nematoda has been investigated and it has been shown that FAR proteins diverged early and experienced low selective pressure to form genus-level diversity.
Abstract: Background Nematodes are a widespread and diverse group comprising free-living and parasitic species, some of which have major detrimental effects on crops, animals, and human health. Genomic comparisons of nematodes may help reveal the genetic bases for the evolution of parasitic lifestyles. Fatty acid and retinol-binding proteins (FARs) are thought to be unique to nematodes and play essential roles in their development, reproduction, infection, and possibly parasitism through promoting the uptake, transport, and distribution of lipid and retinol. However, the evolution of FAR family proteins across the phylum Nematoda remains elusive. Results We report here the evolutionary relationship of the FAR gene family across nematodes. No FAR was found in Trichocephalida species and Romanomermis culicivorax from Clade I, and FAR could be found in species from Clades III, IV, and V. FAR proteins are conserved in Clade III species and separated into three clusters. Tandem duplications and high divergence events lead to variable richness and low homology of FARs in Steinernema of Clade IVa, Strongyloides of Clade IVb, and intestinal parasitic nematodes from Clades Vc and Ve. Moreover, different richness and sequence variations of FARs in pine wood, root-knot, stem, and cyst nematodes might be determined by reproduction mode or parasitism. However, murine lungworm Angiostrongylus and bovine lungworm Dictyocaulus viviparus from Clade Vd have only 3-4 orthologs of FAR. RNA-seq data showed that far genes, especially far-1 and far-2, were highly expressed in most nematodes. Angiostrongylus cantonensis FAR-1 and FAR-3 have low sequence homology and distinct ligand-binding properties, leading to differences in the cavity volume of proteins. These data indicate that FAR proteins diverged early and experienced low selective pressure to form genus-level diversity. The far genes are present in endophyte or root-colonized bacteria of Streptomyces, Kitasatospora sp., Bacillus subtilis, and Lysobacter, suggesting that bacterial far genes might be derived from plant-parasitic nematodes by horizontal gene transfer. Conclusions Data from these comparative analyses have provided insights into genus-level diversity of FAR proteins in the phylum Nematoda. FAR diversification provides a glimpse into the complicated evolution history across free-living and parasitic nematodes.
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 1 |
| 2009 | 1 |