Thursday, January 20, 2011

Love for Snail

Now, for those of you who have accused me of not giving my posts ratings, as per the MPAA, I’m warning you right up front: this post will be about sex. Snail sex.

And, as surprising as this may seem to many of you, there is a lot to tell about snail sex.

Let’s take the charming little creature pictured above, a marine periwinkle of some sort. You wouldn’t know it to look at it (in this picture, at least), but, like all snails, it has its genitalia on the side of its head (thus giving a whole new meaning to the phrase “necking”). This periwinkle is probably one of the many species of snails that, like us, consist of two separate sexes, male and female.

Snails also, like us, have internal fertilization, so unlike those rather sad species that have to cast their seed upon the waters (which seems like no fun at all), they really do have sex. Some species of snails—including periwinkles—can be locked together in a sexual embrace for several hours at a time. (This is what happens when organisms are not as advanced as we are and thus lack jobs or television.)

And then there are the species, like my favorite study organisms, the slipper-shell snails, that change sex—typically in one direction, from male to female. (This allows for a lot of jokes about how, once the snails mature, they become female.) There are many interesting hypotheses and models about the advantages of sex change (in one direction or another), and I could go on about that for a long time (in fact, I did, in my dissertation)—but here I will be brief. Protandrous sex change (that is, being “male first,” then becoming female) is considered an advantage for species where the number of eggs females can produce increases with females’ size while the amount of sperm males produce is the same regardless of their size. So, if you’re a small male, that’s fine, reproductively speaking, but if you’re a small female, you won’t produce as many offspring as if you’re a large female. What better way to achieve peak reproduction at every point in your life than to be male when you’re small and become female once you’re big? (Plus, it must be fun to know what it’s like to be male and female—though that’s not something that’s included in the size-advantage models.)

[the undersides of a bunch of slipper-shells]

The snails stack on top of one another; in one of the species, C. fornicata (yes, that’s really its name), snails live in stacks of up to 20 individuals, with large, female snails near the bottom, sex-transitioning snails in the middle, and males nearer the top. This means that males, while not as well-endowed as barnacles, still have to reach their penes down several snails in order to mate. It also means that there’s all kind of mating going on within the stack; it’s like a little orgy-tower of gastropods.

And then there are land snails! Land snails and slugs are all simultaneous hermaphrodites—they’re both male and female at the same time, all the time. This means that you’re twice as likely to come across a potential mate, leading many people to wonder why humans have such a poor system.

Some species of land snails, though not all, engage in courtship rituals that involve shooting their partner with “love darts,” little calcium-carbonate harpoons that the snails create and extrude. The reasons for love darts, apart from the obvious S&M explanation, are still unclear. The variation in dart forms among species is pretty incredible. (Also, sometimes snails get a little too excited during courtship and shoot themselves in the foot.)

Then there are land slugs, who will meet at night on the underside of a branch and suspend themselves from slime cords—and, hanging there in the moonlight, will intertwine themselves with their partner; each will evert a penis(-like organ) twice the length of their body, which they also intertwine, and they will then exchange sperm from the tips of these organs.

And then there are sea slugs, which are also simultaneous hermaphrodites and who often engage in orgies, daisy-chain style, wherein each individual mates with one slug in the male role and, at the same time, another in the female role.

I could go on and on… But perhaps you’ve had enough excitement for one night.

{A note: I do write all text and take all pictures. Please do not reproduce either without my permission.}

1 comment:

Anca said...

This should have been a Valentine's Day post! Any chocolate involved in any of this? Or is the extraordinary--for us--sex enough?

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