Two new Eubranchus species for Norway

Eubranchus rupium

The identity of two of the more obscure nudibranchs in the Eubranchus family have been confirmed by scientists. Both have been added to the official Norwegian nudibranch list.

Posted on Apr 9, 2013
The two new species now officially on the nudibranch species list for Norway are Eubranchus rupium and Eubranchus doaria. They are both very small, not more than 15 mm, and can be tricky to find.

Even when finding them they can be hard to distinguish from other Eubranchus species, but there are a few tell-tale signs to look for.

Eubranchus doriae (Trinchese, 1874)

This somewhat cryptic nudibranch has some very carachteristic cerata (the tentacles on the back): As is typical for the Eubranchus family they are slightly inflated, and the intestine inside form very characteristic branching "knots" - normally two or three of them.

Eubranchus doria, photographed at Austevoll south of Bergen on the Norwegian west coast in March 2009. This species was found and confirmed at the Nudibranch Safari in March 2013, and is now added to the official species list.

Eubranchus doria is often misidentified as Eubranchus exiguus, but this species normally has just one larger knot in the middle of the cerata. When comparing two specimens of either species the differende is quite clear.

Eubranchus rupium (Møller, 1842)

This nudibranch has longer and more slender cerata than most Eubranchus species, often seen in a bent shape with the tip pointing forward.

It is however the coloration that distinguishes this species from others: At the tip of the cerata a red-brown band made up of tiny pigment specs can be seen close to the white tip.

Eubranchus rupium with the tell-tale red pigmentation on the cerata and back. This specimen also displays nearly mature eggs inside its translucent body. Photo from the Nudibranch Safari in March 2010.

Another tell-tale sign is the branching intestine which can be seen on the back of the nudibranch, especially on the posterior half. The intestine is often reddish in color.

Added to the list

After researching collected specimens as well as photographs, Eubranchus rupium was added to the official species list by scientists Jussi Evertsen and Torkild Bakken a couple months ago.

Eubranchus doriae made its offcial debut after being found during the Nudibranch Safari in March 2013 - although this species has been observed earlier.

On their blog, the before mentioned scientists write more about Eubranchus rupium (Norwegian only).

» Click here to read more about Eubranchus rupium at

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Christian Skauge
Etterstadsletta 4 G
N-0660 Oslo, Norway


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