Abstract
Large parcels of organic matter in the deep sea, such as whale carcasses, harbor a very specialized fauna, most famously the bone-eating worms in the genus Osedax (Annelida, Siboglinidae). Although Osedax was first described only 15 years ago, there are already 26 described species from the Pacific, Atlantic and Southern Oceans. The high discovery rate of new Osedax species indicates that there is still a lot of undescribed diversity. In this study we describe the most northerly species of Osedax to date, Osedax fenrisi sp. nov. from 73°N on the Arctic Mid-Ocean Ridge. We also present an updated molecular phylogeny of Osedax based on COI and 18S, including all described species in the genus. The molecular results support that Osedax fenrisi sp. nov. is distinct from the previously known species of Osedax. Both morphological characters and the molecular phylogeny support the placement of Osedax fenrisi sp. nov. in clade V. The most striking morphological character shared with other described species in this clade (O. rubiplumus, O. roseus and O. bryani) is the presence of long pinnules inserted on the outside of the palps.
Highlights
Large parcels of organic matter in the deep sea such as whale carcasses or sunken wood logs provide nutrients both for opportunistic scavengers and a more specialized fauna (Smith and Baco, 2003; Bienhold et al, 2013)
We present an updated molecular phylogeny of Osedax based on cytochrome oxidase subunit I and 18S rRNA, including all described species in the genus
Osedax belongs to the annelid family Siboglinidae, which is characterized by adult worms lacking a functional digestive system, and instead relying on bacterial symbionts for nutrients (Schulze and Halanych, 2003)
Summary
Large parcels of organic matter in the deep sea such as whale carcasses or sunken wood logs provide nutrients both for opportunistic scavengers and a more specialized fauna (Smith and Baco, 2003; Bienhold et al, 2013). The most famous of the organic fall specialists is probably the bone-eating worms in the genus Osedax (Rouse et al, 2004). Osedax belongs to the annelid family Siboglinidae, which is characterized by adult worms lacking a functional digestive system, and instead relying on bacterial symbionts for nutrients (Schulze and Halanych, 2003). Osedax is unique in having heterotrophic symbionts, which live in the posterior root-like extensions that protrude into the bone substratum and probably utilize collagen from the bones (Goffredi et al, 2005, 2007). Colonization experiments have demonstrated that Osedax are not limited to inhabiting the bones of marine mammals such as
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