21 May 2009

Do hermaphrodite snails have twice the fun?

Over at Deep-Sea News, this week is Sex Week. If you mosey over there, after you finish reading this blog first, you will find many an interesting article providing deep penetration into this most titillating subject matter.

I spend most of my research time studying hermaphroditic gastropods, that is, snails that have both male and female organs. Most terrestrial snails are in the group Pulmonata and all pulmonates are hermaphrodites. Here is a pair of such snails, Oxyloma retusa, mating (details here).


When one is observing a couple of hermaphrodites mating, one naturally wonders if the action is anatomically reciprocal. In other words, whether each snail is deploying its penis. Alternately, one snail could act as a male, while the other as a female. It turns out that in some pulmonates mating is anatomically reciprocal, while in others unilateral (for example, see Davison & Mordan, 2007).

When I was studying the reproduction of Oxyloma retusa, I decided that the easiest way to determine if their mating was anatomically reciprocal or unilateral was by separating a mating pair slowly while watching them closely. By using this forced withdrawal method on many pairs of snails, I eventually determined that in the majority of the pairs mating was anatomically reciprocal. Further details are in my forthcoming paper (Örstan, in press).

Here is a short video that shows the separation of a pair of mating Oxyloma retusa. The snail between the fingers of my left hand was the snail on top or on the right side of the shell of its partner (see the picture above) and the one in my right hand was the snail on the bottom. If you look carefully, near the end of the video you will see the penis of each snail coming out of the vagina of its partner.

One nice thing about this method is that the snails are not harmed.

Davison, A., and P. Mordan. 2007. A literature database on the mating behavior of stylommatophoran land snails and slugs. American Malacological Bulletin 23:173-181.
Örstan. A. Reproductive biology and the annual population cycle of Oxyloma retusum (Pulmonata: Succineidae). American Malacological Bulletin in press.

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