Meeting Abstract
Members of the subclass Enoplia form one of three primary clades in Nematoda. Enoplia includes Enoplida, primarily aquatic nematodes, and Triplonchida, aquatic and terrestrial nematodes. The presence of presumed ancestral features shared with other animals but no other nematodes have led to the suggestion that Enoplia may represent the earliest nematode lineage. A phylogenetic framework for this group allows exploration of the evolution of feeding structures such as fixed teeth, movable teeth and mandibles, among the primary features used in taxonomy and classification. The taxonomy of Enoplia has been turbulent in recent years, with several families being transferred from Enoplida to Triplonchida and the placement of certain taxa remaining unclear. This study aims to expand taxonomic sampling, clarify relationships, and evaluate hypotheses of homology and evolution of feeding structures within Enoplia. Nearly full-length 18S (SSU) rDNA sequences were determined for members of Enoplia, and phylogenetic trees using maximum likelihood and Bayesian analyses were inferred. Preliminary analyses suggest that fixed teeth and movable mandibles evolved from movable teeth. Several members of Triplonchida (Tobrilina and Tripylina) were shown to be nested within Enoplida, and at least one genus in Enoplida, Viscosia (Oncholaimidae), appears to be paraphyletic. Clarifying relationships and expanding knowledge of Enoplia will aid in homology assessment of feeding structures and determination of features needing deeper morphological investigation.
