Diversity of Norwegian sea slugs (Nudibranchia): new species to Norwegian coastal waters and new data on distribution of rare species

A total of 5 nudibranch species are reported from the Norwegian coast for the first time (Doridoxa ingolfiana, Goniodoris castanea, Onchidoris sparsa, Eubranchus rupium and Proctonotus mucroniferus). In addition 10 species that can be considered rare in Norwegian waters are presented with new information (Lophodoris danielsseni, Onchidoris depressa, Palio nothus, Tritonia griegi, Tritonia lineata, Hero formosa, Janolus cristatus, Cumanotus beaumonti, Berghia norvegica and Calma glaucoides), in some cases with considerable changes to their distribution. These new results present an update to our previous extensive investigation of the nudibranch fauna of the Norwegian coast from 2005, which now totals 87 species. An increase in several new species to the Norwegian fauna and new records of rare species, some with considerable updates, in relatively few years results mainly from sampling effort and contributions by specialists on samples from poorly sampled areas.