Unknown sea slug - does anyone know?

About a month ago I captured this image of a pleurobranchid ophistobranch at Gulen Dive Resort. Is has so far been impossible to identify. Do you know what species this might be?

When discovered, this strange sea slug was feeding on a Corella parallellogramma sea squirt.

By Christian Skauge   Published: May 26, 2011

The almost translucent sea slug was sitting at a Corella parallellogramma sea squirt at approximately 17-18 meters, possibly feeding on it. At first glance I just noticed that the ascidian was a little strange-looking, and I was on my way to move on.

However, experience has taught me to always have a second look when something appears "strange".

I did, and my first thought was "wow, is that some sort of squid?" but then I realized it had to be a sea slug. The question is - what species?

Is it a Berthella?

The specimen was quite large, around 3 centimeters long, and when moved to a more neutral background it soon became apparent that it had the characteristic siphon of the Pleurobranchs.

It also had two rhinophores, suggesting it might be a Berthella species. The foot was particularly large and extended well beyond the mantle on both sides.

I asked the help of nudibranch experts Jussi Evertsen and Torkild Bakken at www.nudibranchia.no, and they confirmed the initial suspicions that it might be a Berthella species.

Very little research has been done on this family in Norway, and the only species reported here are Berthella sideralis, B. plumula and B. citrina. This one does not match the appearance of any of them!

The specimen was collected and delivered to the experts, and it is my hope that further studies of the internal shell or DNS barcoding will reveal what this really is.

No help online, so far

Extensive research on the internet has lead me nowhere. I have looked through every image of Pleurobranchs at www.seaslugforum.net but have found nothing that matches - except maybe one or two species found in New Zealand.

Unfortunately, Seaslugforum is inactive for the time being, so I cannot get an opinion from nudibranch expert Bill Rudman.

I have now posted the image on www.nudipixel.com in the hope that anyone there will be able to help.

The difficulties in identifying it suggests this might be a new species to Norway, but it might be registered, or indeed common, in more southerly (or even northerly) waters.

Do you know which species this might be, or have you perhaps seen something similar? If that is the case, I would love to hear from you!

» Any idea what this is? Please get in touch!

Telephone: +47 94 83 32 83
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Christian Skauge
Etterstadsletta 4 G
N-0660 Oslo, Norway


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