New and known species of the genus Desmodora De Man, 1889 (Nematoda: Desmodoridae) from the hydrothermal vent communities of the Piip volcano (south-west Bering Sea)

Species of the marine nematode of the genus Desmodora have been found to dominate (up to 78%) in the nematode fauna from the hydrothermal vent communities of submarine Piip volcano, Bering Sea. The morphological characteristics and molecular genetic data of Desmodora specimens from different habitats of the volcano were studied and three new and one known species have been described: Desmodora hydrothermica sp.nov., Desmodora marci, Desmodora spongiophila sp.nov., Desmodora spongiocola sp.nov. The species often lived together, but a pronounced spatial specialization was observed. Desmodora spongiophila sp.nov. and Desmodora spongiocola sp.nov. were abundant inhabitants of the vulcanellids and some hexactenellids. Desmodora hydrothermica sp.nov. dominated in microbial mats on the carbonate chimneys from the South Summit, while Desmodora marci was found on stones near vents and in bottom sediments with Calyptogena pacifica (Bivalvia: Vesicomyidae). The last two species were already known in deep-sea reduced environments of the Pacific and Atlantic oceans, in similar habitats. The δ¹³C and δ¹⁵N values and fatty acids composition of Desmodora samples from hydrothermal habitats confirmed the consumption of chemosynthetically derived organic matter. SSU and D2-D3 of LSU phylogenetic trees largely agree with those of previous analyses indicating that Desmodora is not monophyletic. Moreover, phylogenetic relationships within the subfamily Desmodorinae remained unresolved.