Nudibranch diversity (Gastropoda, Heterobranchia) along the coast of Norway

Based on available information on nudibranchs from all published literature, sampling concentrated around the area of Central Norway, and the nudibranch collections at the Museum of Natural History and Archaeology in Trondheim, this study presents the distribution of nudibranch species along the Norwegian coast. All species reported in the literature from Norwegian waters are listed and discussed. A total of 81 species are confirmed being a part of the Norwegian fauna, of which four species (Cuthona rubescens, Polycera faeroensis, Eubranchus vittatus and Onchidoris depressa) are new to Norwegian waters, and two that have previously been mentioned but not documented, Cuthona caerulea and Geitodoris planata, are confirmed found for the first time. Six species, Triopella incisa, Cadlina glabra, Rostanga setidens, Cuthona distans, Cuthona norvegica, Berghia norvegia are considered endemic to Norway, and four species, Doridunculus echinulatus, Doris nobilis, Doto crassicornis, Goniaeolis typica are considered endemic to Scandinavian waters. After the review six species previously reported from Norwegian waters, are considered insufficiently supported, or due to misidentifications (Onchidoris aspersa, Onchidoris oblonga, Onchidoris sparsa, Thecacera virescens, Doto tuberculata and Flabellina browni) and are not longer considered a part of the Norwegian fauna. Sampling has in large been based on SCUBA diving, and proved to be very efficient when sampling in the upper sublittoral in kelp forest habitat.