Desmotersia levinae, a new genus and new species of free-living nematode from bathyal oxygen minimum zone sediments off Callao, Peru, with discussion on the classification of the genus Richtersia (Chromadorida: Selachinematidae)

Desmotersia levinae gen. n., sp. n. is proposed, based on material found in bathyal oxygen minimum zone sediments off the coast of Peru. Desmotersia closely resembles Richtersia in the animals’ general appearance and in spiny ornamentation of the body cuticle, but clearly differs in stoma structure and by the presence of a dorsal tooth. The systematic positions of the two genera are discussed, since Desmotersia apparently forms a link between Selachinematidae and Desmodoridae. Desmotersia levinae is characterized by a variety of spiny ornamentations anteriorly formed by bipartite spines arranged into a fin-like picket fence, by a head with an asymmetrical cephalic capsule, presence of two closely spaced ventral longitudinal rows of copulatory thorns, and by 2–4 ventral thorns in mid-tail positions on the male. The interaction between the new species and its habitat is discussed.