A revision of the Oligobrachiidae (Annelida: Pogonophora), with notes on the morphology and distribution of Oligobrachia haakonmosbiensis Smirnov

Abstract

The present study is based on new material of Oligobrachia haakonmosbiensis from the Arctic and Northeast Atlantic. The species redescribed here is shown to have a wider distribution than previously known. The investigation of well-preserved specimens of O. haakonmosbiensis revealed longitudinal glandular patches on the forepart, which previously have not been observed due to inadequate fixation. In addition, the opisthosome is described. The presence of glandular patches confirms the closest morphological affinity between O. haakonmosbiensis and O. webbi, the two North Atlantic pogonophorans of the genus Oligobrachia. These two species are unique among Oligobrachia species in possessing cuticular plaques on the anterior (metameric) part of the trunk and in lacking pinnules on the tentacles. The description of O. dogieli is supplemented with a few important details. Key characters of all species of the genus Oligobrachia are given in a table. It is suggested that the family Oligobrachiidae includes four genera: Oligobrachia, Nereilinum, Unibrachium and Polarsternium; their species are listed and diagnoses reviewed. The peculiar characters of Crassibrachia and Birsteinia which allow me to exclude these genera from the family are listed. Two keys are provided to the oligobrachiid genera and to the known world species of the genus Oligobrachia.

Key words:

• Morphology
• Oligobrachia
• Pogonophora
• review

Acknowledgements

I thank the crews of the RVs Håkon Mosby (cruise 16, 1995), Professor Logachev (cr. 15, 1996), Polarstern (cr. 19, 1991; cr. 36, 1995; cr. 51, 1998) and Pourquoi-Pas (Vicking cr., 2006) for the opportunity to study the Arctic and North Atlantic pogonophorans. My special thanks are due to Dr Andrey Gebruk (P.P. Shirshov's Institute of Oceanology, Moscow) and Dr Ann Andersen (HERMES: Hotspot Ecosystem Research on the Margins of European Seas) for their support.

Editorial responsibility: Danny Eibye-Jacobsen