Colour variation in Hermissenda crassicornis

April 4, 2007
From: Carissa Thomas

Hi there!

I recently took a trip to Neptune State Park, Oregon and photographed a nudibranch that I'm almost sure is Hermissenda crassicornis (shown in the upper photo ). Finding this one made me question the photo I had already had on file for Hermissenda. This one was taken on North Beach, Orcas Island, Washington (lower photo ). Are these just different color variations of H. crassicornis, or is one a different species?

Thanks for your help!
Carissa Thomas
Seattle, WA

Carissa.Thomas@gmail.com

Thomas, C., 2007 (Apr 4) Colour variation in Hermissenda crassicornis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19786

Hi Carissa,

Your identification is quite correct, as is your speculation that Hermissenda crassicornis is a variably colored species. In the first edition of "Pacific Coast Nudibranchs" I was able to present all three color extremes, which include both of yours shown here. Your top photo, showing a white line extending up each cerata to the tip, is very characteristic of the most common coloration seen in Oregon, Washington and British Columbia. Your lower photo is a juvenile, recognizable but the orange elongate rhomboid patch on the animals head outlined with a white line (in adults it would be pale blue). The third color variant, more commonly observed in the southern reaches of this species range (ie: California) has orange ceratal cores with a white tip. This is the form shown in my "Eastern Pacific Nudibranchs." All three have the characteristic lines on the head tentacles, medially to the tail, and along the margin of the foot.

Thanks for bringing this important variation up,
Dave Behrens

Behrens, D.W., 2007 (Apr 4). Comment on Colour variation in Hermissenda crassicornis by Carissa Thomas. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19786

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Hermissenda crassicornis

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