Mating Slugs: Courtship - Type A

I'm now going to discuss the second part of the precopulatory period, as I've defined it: courtship. (Remember, if you're referencing Reise's article on Deroceras that I mentioned previously, I've had to re-divide the mating process to fit the behavior of Lehmannia valentiana, so I'll hardly address precourtship at all. I've lengthened courtship to include trail following.) Courtship varies by couple, however it's possible to categorize behavior into a few general groups. This post will deal with the first type, Type A.

Type A: Common behavior, usually successful. In precourtship, two slugs investigate each other with their cephalic tentacles. At the beginning of courtship, one slug turns around, becoming the leader, and the other follows on the former's tail; the lead slug picks the mating site, turning back towards the follower as they begin to circle each other, aligning their gonopores. The journey to the mating site can be quite long; in fact, it can be a real cross-country trek sometimes. As slugs mate on a variety of surfaces, I don't know what criteria go into choosing a mating site, just as I don't know what criteria are involved in selecting a partner.

To illustrate the first and most common type of courtship among Lehmannia valentiana, I'll be showing photos of Couples 1, 6, 11, and 15.

Couple 1:

Couple 6:

This is the final segment of courtship, in which the partners mouth one another, nibbling mucus. You can already see white forms beneath the surface of each slug's side, below the mantle; these are the genitalia and sperm masses ready to emerge. Later I will show photos of the penial appendices, which are everted at the very end of this segment.

Couple 11:

Couple 15:

When contact is broken, it's not necessarily resumed. Many times trail following will cease and mating never takes place. Fortunately this pairing turned out to be successful. 

I hope that you've been able to notice a pattern here: first trail following, then selection of mating site, then circling, then mouthing/nibbling and entwining. These are the characteristics of Type A Courtship in Lehmannia valentiana. Now, I still hesitate to call it courtship, as it differs markedly from that observed by Reise in Deroceras, in which a veritable battle takes place between partners, each with its sarcobelum extruding, attempting to touch the other with its mouth or sarcobelum, and waving its tail and lunging. Courtship in Lehmannia valentiana is much more peaceful; I've never witnessed any behavior of that sort in them.