Ryuguderes casarrubiosi sp. nov., a new deep-sea representative of the enigmatic genus Ryuguderes (Kinorhyncha: Cyclorhagida: Campyloderidae) from the Indian Ocean

Abstract

A new species of the rare genus Ryuguderes is described from a deep-sea muddy seafloor part of a cold seep area at the Mozambique Channel (western Indian Ocean). The new species is easily distinguished from its only known congener by the arrangement of the middorsal (segments 2–9 in Ryuguderes iejimaensis vs. segments 1–10 in the new species) and the lateroventral acicular spines (segments 4 and 6–9 in R; iejimaensis vs. segments 3–4 and 6–9 in the new species) as well as the ventromedial female papillae (segments 6–7 in R. iejimaensis vs. segments 6–8 in the new species). Despite the ecological peculiarities of the habitat where the new species was found, all the examined specimens were recovered outside any active pockmark, which could point towards a lack of adaptation to the extreme environmental conditions associated with cold seeps.