New species of Siboglinum (Annelida: Pogonophora) from the Antarctic Ocean

Abstract

Four new species of the genus Siboglinum Caullery, 1914, obtained from 12 stations at depths of 1265–6070 m in the Atlantic and Indian Ocean Sectors of the Antarctic Ocean are described. The material came from the following regions: Scotia Sea, Weddell Sea, Bransfield Strait, Orkney Trench, Laurie Trench and Davis Sea. The comparative characteristics of the new species are given in a table. Several characters occurring in various of the new species are rare or unique among the congeners: cuticular plaques on the metameric region of the trunk, four separate girdles of chaetae, an extremely long distance (up to 7 mm) between the girdles, occurrence of a transverse row of interannular papillae, a remarkable leftward shift of the tentacle base, and a combination of both main types of arrangement of postannular papillae (in rows and singly) within one species. The new species are assigned to two subgenera, Siboglinum Caullery, 1914 and Ekmanifilum Smirnov, 2014; the diagnostic characters of all Siboglinum subgenera are compared and summarized in a table. Two keys are provided to the Siboglinum subgenera and to the known species of Antarctic pogonophorans.