The Pleurobranchidae sea slug species Berthella sideralis was described by the Swedish malacologist Sven Ludvig Lovén in 1846 based on specimens collect at Bohuslän, in southern Sweden not far from the city of Gothenburg. This species has hardly been mentioned in the literature after its original description, and no images of life species are to our best knowledge available in books, research papers or even web platforms – until now!

A synthesis of the morphological features of B. sideralis can be found in Cervera et al. (2010) who studied in detail two specimens collected during 1930’s in Trondheimfjord as part of a phylogenetic study of the genus Berthella.

Recently, in late November 2015 during a Museum scientific cruise – there is a blog post about this day of field work here – we collected one specimen in Hjeltefjorden (around Bergen) at 220 meters depth using an RP-sledge. This specimen is here documented and was recently genetically barcoded as part of our effort to barcode the Norwegian marine fauna through the NorBOL project.

A live specimen of Berthella sideralis. The scale bar i 5 mm. Photo: K. Kongshavn

Berthella sideralis is only known from Sweden and Norway. In Norway it has been reported between Bergen and Finnmark.

Reference: Cervera, J L., Gosliner, T. M., García-Gómez, J. C., & Ortea, J. A. 2010. A new species of Berthella Blainville, 1824 (Opisthobranchia, Notaspidea) from the Canary Island (Eastern Atlantic Ocean), with a re-examination of the phylogenetic relationships of the Notaspidea. Journal of Molluscan Studies, 66: 301–311.

-Manuel & Katrine