23 May 2005

Deroceras reticulatum mating

Inspired by the story and a photo of mating Limax maximus at bootstrap analysis , I am presenting an account of the mating of another alien slug from Europe, Deroceras reticulatum (also known as Agriolimax reticulatus).

Like Limax, Deroceras is also a hermaphrodite with each slug normally bearing both female and male organs. However, unlike Limax, Deroceras mates on the ground. They have relatively large penises that they carry inside their bodies and which are everted during mating. The penis has a multi-lobed appendage in addition to a peculiarly shaped stimulator organ (sarcobelum).

Although they are stated to mate usually at night, once I observed them mating at noon in my backyard. Detailed descriptions of their mating behavior have been published1, 2. During courtship, which may take an hour or more, the slugs very slowly turn around in a circle while stroking each other with their sarcobela protruding from their genital openings. You can see the worm-like sarcobela in the picture on the left.

During the actual mating, they don't insert their penises into their partners' vaginas, but exchange sperm externally. In the picture on the right their penises appear to have been fully everted and intertwined. The arrows are pointing at what seem to be the appendages on the penises. This phase of the process takes a relatively short time and after which the slugs separate.

Here is a question for the readers to think about: why do these slugs always circle each other clockwise during courtship?

1. Karlin, E.J. & Bacon, C. 1961. Courtship, mating and egg-laying behavior in the Limacidae.
Transactions of American Microscopical Society, 80:399-406.
2. Webb, G.R. 1961. The sexology of three species of limacid slugs. Gastropodia, 1:44-55 .

1 comment:

Nuthatch said...

Glad you saw the Limax post! I was going to drop you a line (no pun intended) to bring it to your attention. I'm pleased it is worthy of a mention in the blog of a slug expert.