The distinctive name may be hard to pronounce, and comes from the old name for the area of Ørlandet – yrjar, where the sea slug was first found, the Norwegian name for yellow, gul – yrjargul!

The new nudibranch was found by divers Kjetil Johnson and Viktor Vasskog Grøtan outside Ørlandet west of Trondheim in 2014, and was posted on the NE Atlantic Nudibranchs group on Facebook.

Nobody could tell them what species it was, and it's very unusual to find a large nudibranch (up to 10 cm) that hasn't been spotted before. Since then, work to describe the species scientifically has been going on.





Norway's coolest nudibranch?

– I think it's the coolest-looking nudibranch we have in Norway. We have been waiting eagerly for the paper to be published in the last few weeks, Viktor Vasskog Grøtan tells Dykking magazine.

The new species was published a couple of weeks ago in the scientific journal «Contributions to Zoology», and the name Dendronotus yrjargul was officially entered into the annals of biology.

Kjetil Johnson and Viktor Vasskog Grøtan have found the nudibranch numerous times outside Ørlandet, and also contributed to the scientific paper. Now they will live forever in nudibranch history as co-authors of the paper describing this species.

See video of the new nudibranch:





Valuable cooperation

– Once again we see the importance of cooperation between divers, underwater photographers, and scientists. This is an excellent example of what citizen science can achieve, Torkild Bakken writes on his nudibranch blog.

In addition to the two nudibranch enthusiasts, authors of the paper are Torkild Bakken from NTNU Museum of Science, Kenneth Lundin from the University of Gothenburg in Sweden, and Tatiana Korshunova and Alexander Martynov from the University og Moscow.

The scientific paper also looks at the Dendronotus genus. Several changes have been made here over the last few years, and new species have been described – among others, Dendronotus europaeus from Norway three years ago.