Aplysia mating chain

May 9, 2000
From: Bill Rudman

Here is a photo of three Sea Hares [Aplysia dactylomela] mating. By chance we were testing a new digital camera when these animals, which had been collected for public display, decided to ignore the audience and give us something to photograph. PHOTO: Alison Miller.

Sea Hares, like all sea slugs, are hermaphrodite, which means they have a fully functional set of male and female reproductive organs. During mating they can operate as both male and female simultaneously. This is somewhat difficult to achieve when there are only two animals, because the penis is just to the right of the head, and the vagina opens into the mantle cavity between the large parapodia.

Sea Hares, however, commonly occur in quite dense populations and this often leads to a number of animals mating together. The usual method of mating is for the 'male' partner to crawl onto the back of the 'female' partner and the push its head between the parapodial flaps so that its everted penis can enter its partner's vagina. Mating chains occur when a third animal decides to mate with a Sea Hare already acting as a 'male' partner by crawling on its back and inserting its penis. Chains of 4 or 5 animals can at times be found in nature, and in crowded aquaria, even longer chains can form. In these mating chains, the first animal in the chain acts only as a female, and the last acts only as a male, but all the other animals are acting simultaneously as males and females.

Bill Rudman.

Rudman, W.B., 2000 (May 9) Aplysia mating chain. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2370

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