Unknown stowaway on Caulerpa

September 3, 2002
From: James Stein

I recently purchased some Caulerpa from a marine store in Tampa, Florida [USA]. I have no idea where the algae came from but I would suspect off the coast of Tampa somewhere. I was pleasently suprised to find one of these critters in my tank after putting the algae in it. Much to my suprise I've counted now a total of 5 of them and they are literally covering every surface they can find with spirals of green eggs. They are all about 1 inch to 1 1/2 inches in length now and have a habit of entwining themselves in groups of 3 or more. I'm interested in finding out exactly what they are. They aren't particularly pretty or colorful but are still quite interesting to watch. Any help would be greatly appreciated.
James Stein


Stein, J., 2002 (Sep 3) Unknown stowaway on Caulerpa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7875

Dear James,
Your little animal is the Caribbean species Oxynoe antillarum. It feeds on Caulerpa, so that is obviously how it arrived in your aquarium. If you can take a photo of the egg masses it would be a nice addition to the Forum.

They have a transparent shell which is hidden between the two flaps of skin [parapodia] behind the head. Oxynoe is a sacoglossan sea slug, a group which includes the shell-less Elysia crispata which you may be familar with. All sacoglossans feed by stabbing a hole through the cell wall of the algae that they feed on, and then sucking out the cell contents.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Sep 3). Comment on Unknown stowaway on Caulerpa by James Stein. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7875


Oxynoe antillarum

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