Re: Sea Hares - mating chains

July 9, 1999
From: Sigrid Schmalzer

I am a volunteer at the Birch Aquarium in La Jolla, California (affiliated with the Scripps Institution of Oceanography) where I provide interpretation at the touch tanks. The California Sea Hares (Aplysia californica) in one of the tanks were mating today. Their position was very similar to that of the Sea Hares in the photos supplied by Erwin Koehler. I was amazed by how long they remained engaged -- several hours at least. They were not disturbed by gentle touches by the visitors, and the sea hare receiving sperm continued to "beg" and feed on Ulva (sea lettuce) offered by visitors.

Regarding the begging behavior, the Sea Hares placed in the touch tanks learn quickly that food comes from above. When tickled lightly on the head, they wave their heads and even open their beautiful mouths to receive Ulva (see photo). The wild Sea Hares I have found in nearby La Jolla Cove do not react at all to this kind of stimulus.

Despite their reputation for being fragile, the California Sea Hares do very well in the touch tanks. (Of course, we're very protective of them and ensure they're treated respectufully.) I have watched several grow from finger size to forearm size in the tanks.

This is a very good year for Sea Hares in this area. Visitors to La Jolla Cove have had a very easy time finding the Black Sea Hares (Aplysia vaccaria), and I found one California sea hare on my last visit.


Schmalzer, S., 1999 (Jul 9) Re: Sea Hares - mating chains. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Sigrid,
Thanks for the interesting information on Sea Hares and the great photo of Aplysia with a mouthful!. By coincidence I have just had an enquiry from Eileen Steger about a 'black football-shaped' animal washed up on the beach in California which I guess is Aplysia vaccaria. If by chance you have a photo of Aplysia vaccaria it would be nice to be able put one on the Forum.

I have never heard of anyone 'training' Sea Hares like this for touch tanks, but obviously their use for scientific studies in learning and brain function suggests they can be taught simple things. As I'm sure you know, touch tanks are a great way for kids (and parents) to experience and discover why we find marine life so fascinating.

Best wishes,
Bill Rudman.

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