A re-description of the enigmatic deep-sea holothurian Irpa abyssicola (Elpidiidae, Elasipodida) with remotely operated vehicle observations on benthic organisms in the Norwegian-Greenland Basin
The deep-sea holothurian Irpa abyssicola (Elpidiidae) has been re-discovered in the Norwegian-Greenland Basin after more than 100 years. The remotely operated vehicle Victor 6000 was used to collect specimens and to make observations on the biology (density, distribution and behaviour) of the benthic megafauna during a dive to the Hayes Deep (maximum depth ca. 3700 m). The specimens of Irpa abyssicola were in exceptionally good condition, allowing a re-description of the species. The original description of the holothurian was found to lack many significant morphological details. In particular, it is clear from the new specimens that three pair of dorsal papillae fuse to form a velum in an anterior third of the body. There are no separate dorsal papillae, as described originally.