Sammendrag
Six species of Ophelina Ørsted, 1843 have been identified in an extensive material covering 145 localities from 575 to 3900 m depth in the Nordic Seas. Ophelina opisthobranchiata Wirén, 1901 and O. helgolandiae Augener, 1912 were recorded for the first time since their original description about a century ago. O. opisthobranchiata was the most abundant species with more than 18,000 collected specimens. It was recorded between 800 and 3900 m depth and was the only species of Ophelina found deeper than 2000 m. Ophelina cylindricaudata (Hansen, 1879) and Ophelina abranchiata St?p-Bowitz, 1948 were both widespread from 600 to about 2000 m depth. A new species, Ophelina brattegardi sp. nov., is described from off East Greenland, and another presumably new species, Ophelina ?B?, from shelf break areas off western Norway is diagnosed but not formally described due to insufficient material. O. cylindricaudata and O. abranchiata are redescribed based on type material and newly collected specimens. Ammotrypane minuta Annenkova, 1952 from deep water in the Greenland Sea is newly synonymised with Ophelina helgolandiae. Descriptions are also provided for O. opisthobranchiata and O. helgolandiae. The present study illustrates the importance of examining a relatively large amount of specimens in order to correctly establish characters of fragile structures such as branchiae and anal tube. It is also shown that the number of setigers is stable for all recorded species and consequently represents a character of taxonomic importance.
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