Hermissenda crassicornis from Oregon, USA

June 3, 2006
From: Julie Gilchrist

I noticed this curious creature in a shallow beach tidepool this weekend in Oregon.

Locality: Cannon Beach, 6 inch tidepool, Oregon, USA, NW Pacific, 30 May 2006, sandy tidepool on beach. Length: 1 inch. Photographer: Julie Gilchrist.

Any ideas on what it is?
Thanks!
Julie Gilchrist

jules@thisjourney.com

Gilchrist, J., 2006 (Jun 3) Hermissenda crassicornis from Oregon, USA. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16753

Hi Julie,
Thanks for thinking of us with your request.  You have found one of the prettiest aeolid nudibranchs on this coast.  This is Hermissenda crassicornis.  Some folks use the common name - Opalescent sea slug, but I prefer to avoid these.

Although the coloration of the cerata varies with locality, the one characteristic that is always present is the thin romboid shaped patch of orange, outlined with white, just behind the rhinophores. The white may be flanked with blue, which can also be found along the edge of the foot and medially on the tail.

This species grazes on hydroids, both in tidepools and subtidally.

Thanks
Dave Behrens

Behrens, D.W., 2006 (Jun 3). Comment on Hermissenda crassicornis from Oregon, USA by Julie Gilchrist. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16753

Factsheet

Hermissenda crassicornis

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