First account on the diversity of Ophryotrocha (Annelida, Dorvilleidae) from a mammal-fall in the deep-Atlantic Ocean with the description of three new species

Abstract

Annelids of the genus Ophryotrocha are globally distributed in a wide variety of organically enriched habitats. Although mostly known from shallow water, the expansion of deep-sea research revealed several new Ophryotrocha species mainly associated with organic-falls, in particular with cetacean carcasses, or whale-falls. Despite the great deal of interest that fauna associated with whale-falls have attracted, very little is known about this fauna in the deep-Atlantic Ocean. Hereby we analyse, for the first time, the Ophryotrocha assemblage associated with a mammal-fall in this region of the world’s ocean. Specimens were collected from the bones of degrading cow carcasses deployed in the Set ubal canyon at approximately 1000 m depth. Using morphological characters and phylogenetic analyses based on the nuclear gene H3 performed on 31 Ophryotrocha species, we report the presence of five different species, we describe three new species and extend the distribution of O. scutella. Ophryotrocha scutella was previously known from a shallow-water whale-fall and organically enriched sediments beneath a fish farm off Scandinavia and is the first species to be reported from organic-falls in both shallow and deep waters. The presence of five congeners emphasize the importance of the genus Ophryotrocha in the degradation of organic matter in the deep-sea. Our results substantially increase the number of deep Atlantic species in the genus Ophryotrocha and highlight the remarkable unknown diversity and biogeographic patterns hidden behind unstudied deep-sea habitats.