Cross-species mating

March 8, 2003
From: Samuel K. Moore

I'm new to the site, but a former Aplysia californica researcher. I've often wondered whether the prevention of cross-species mating had something to do with a chemical attractant exuded during egg-laying. Some research by my former boss, Earl Mayeri (UCSF) showed that contact with an egg-mass led to both egg laying behavior and mating as a female as well as the attraction of other Aplysia to the orgy. We always suspected some pheromone from the atrial gland led to all this. Anyway, I wonder whether cross-species mating might have to do with two species having similar pheremones. In contrast, perhaps speciation could arise by mutations in the pheromone gene. Just a thought.

Does anyone know if anyone has looked at this issue in closely related or geographically colocated species?

Dear Sam,
Welcome to the Forum. I would agree that species identification problems, both in mating and in 'trailing' would seem to be related to an inability to differentiate some chemical marker the slugs produce. However I don't know of any work on this. These 'mistakes' have only been reported a few times. If this means they are uncommon events I guess they are not a good subject for a research project which needs a completion date.

Concerning your work on Aplysia. I remember a paper on the topic (Bernheim & Mayeri, 1995) and a related paper which I saw publicised somewhere as the Sea Hare Love Drug which I'll summarise in a separate message. There is so much work that has been done on Aplysia californica in the last 20 years that we need a new book synthesising the results to put on the shelf alongside Eric Kandell's pioneering works.

• Bernheim, S.M., and Mayeri, E. (1995) Complex behavior induced by egg laying hormone in Aplysia. J. Comp. Physiol. 176: 131-136

Best wishes,
Bill Rudman

Rudman, W.B., 2003 (Mar 8). Comment on Cross-species mating by Samuel K. Moore. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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