Snail Porno - How Slipper Snails Do IT

As a side project in the lab we have been making snail porn (here for full YouTube video).  Trying to get photos or videos of our snails in the act, doing the deed, getting it on... or as we say in lab, copulating or mating.

The last post described how to tell the sex of slipper snails.  Just like lots of animals males have a penis and females have an opening that receives the penis and the sperm.  But, something we would like to know is how exactly does this transfer happen?

The snails are shy and seeing what's going on is easier said than done.  

You can see the penis from the male Crepidula fornicata extending under the shell of the female he is stacked on.

The common idea that slipper snails have to be stacked one on top of the other to mate is not always true.This small Crepidula onyx is extending his penis across the substrate to the female. 

From observations of snails in cups like these we know that mating can last for hours.  Snails are slow, but what is going on under there for all that time?  Recently Matt Starr, a student in the lab, was lucky enough to get this footage of mating in a pair of snails that had been detached from the substrate.

Here the male is just exploring, prior to copulation.

To most people it probably seems that as long as mating happens and successfully produces offspring it's not really important exactly how.  But the details of copulation can shed light on some important questions in evolutionary biology and behavioral research.  For example:  Can females control who they mate with? Why do females mate more often than necessary to fertilize their eggs?

If they mate with more than one male, can females manipulate whose sperm they use to fertilize their eggs? 

Copulation!

We already knew, from anatomy that sperm is passed to the female in an open groove that runs to the end of the penis.  Unfortunately we can't see the sperm moving in the videos.

But we can see that there is a lot of activity on the part of both the male and female.  We can see is that the long thin papilla at the end of the penis inserts into the female genital papilla.  That's not so surprising, but makes us wonder what happens in the many species that lack both the female genital papilla as well as thin extension of the penis.

So far Crepidula incurva is the only species for which we've obtained video.  We hope to find out how copulation differs across species with different penis morphologies and why mating takes so long.  In some animals the male uses his penis to displace sperm that were deposited by previous males, could this be what's taking so long when Crepidula mate?