Malacology 101: Snail Sex

CW: NSFW snail facts.

Those who know me well know that I adore snails. Malacology – the scientific study of gastropods such as slugs, snails, and mollusks – has become a serious area of interest for me over the past year or so. My fascination with malacology began when I attempted to create my own biosphere (a contained, self-maintaining habitat for aquatic plants, mosses, and microscopic critters); one of my aquatic plants came with a tiny bladder snail (Physella acuta - AKA pest snail, or freshwater pond snail). I became utterly enamored with the tiny, adorable bladder snails until they bred so fast that I couldn’t keep up with them…they ended up eating literally all my water plants, so I needed to get rid of them. It turns out that they’re a common problem for aquarium keepers (and had I done my research, I would have known that). I decided that once I have the appropriate space and time to maintain an aquarium, I’ll probably keep larger aquatic snail species (ones that won’t procreate like crazy).

My appreciation for snails was quelled until I got another opportunity to keep them – this time, with terrestrial snails. One night, I received a message from a friend of mine, stating that he found a garden snail in the dumpster of the restaurant he was working at. He sent me a picture of the snail, asking if I wanted to keep it. An hour later, I bought a terrarium, a food dish, and found a pot for it to hide in, as well as some substrate, plants, and a stick for it to climb on – a pretty comfortable environment, when compared to a dumpster. I found out that it was a grove snail (Cepaea nemoralis), and I named it Biggie Snails.

Biggie Snails, about to investigate some carrots. 

Keeping garden snails is fun; they’re relatively low-maintenance and easy to care for, while being incredibly adorable and fascinating to learn about. However, like the bladder snails I mentioned above, most garden snails procreate very quickly. I wasn’t aware of this at first (again, I only did the bare minimum of research here) until I witnessed Biggie burrowing into the substrate, laying a full clutch of eggs.

Snails like to burrow down into the substrate (soil), to protect their eggs from predators. Here, Biggie chose to lay its eggs right beneath the food dish. 

Snails and slugs are hermaphrodic - they possess both male and female genitals. They prefer to mate and exchange their "genetic stuff" with others (which produces healthier stock), but if that isn't an option, some species can fertilize their own eggs. I’m unsure if grove snails prefer to mate with others or not; either Biggie had already mated with another prior to finding its way into a dumpster (sad), or it inseminated itself. At any rate, within a few weeks, I had at least 50 baby snails crawling around in the habitat I made for Biggie.

One of Biggie's babies, exploring the log in the tank. Notice how translucent it is; this one is only 5-7 days old.

A baby snail, exploring my thumb. Here, its shell is still somewhat see-through, but the brown stripes characteristic of grove snails are beginning to form. This one is about 2 weeks old.

The baby snails start out totally translucent; they need a lot of calcium in order to grow their shells properly (most terrestrial snail keepers use ReptoCal or a cuddlebone in their tanks; I’ve found that both work rather well). Unfortunately, only 15-20 of Biggie’s baby snails survived. Of those, I kept only one – Missy Shelliot – and I set the rest free into the wild. I have mixed feelings about setting them free; grove snails are an invasive species already (they came along on vegetable ships with European colonizers), and I don’t want to screw up the natural order. I set one snail free in different locations, with each location being 7-10 miles away from each other.

Missy Shelliot, who seems to enjoy exploring new places a lot more than Biggie does. 

I mentioned that snails need calcium for maintaining their shells; here's a good example of why. Missy Shelliot's shell is on the left, and Biggie Snails's shell is on the right. Biggie's slime isn't as strong as it used to be (he's getting rather old now), so he falls from the lid of the terrarium sometimes. This caused significant damage to its shell, exhibited by flaky white fragments in the middle of the spiral. Fortunately, though, the shell is beginning to grow back, due to the fact that Biggie is finally starting to notice the cuddlebone that I left in their terrarium.

Earlier this week, I caught both Missy Shelliot and Biggie Snails in the mating act. Slugs and snails display elaborate mating rituals that last for hours, which are specific to certain species. Supposedly, this keeps them from mating with other species and prevents them from making hybrid babies. Snail mating is equally fascinating as it is gross; they start off as if they’re about to argue, fight, or dance, but with their genitals out. Most snail species inseminate each other at the same time, both giving and receiving sperm. Some slug species also do this, but in slightly more entertaining ways – for example, great grey garden slugs can copulate in midair, suspended from strands of slime that can be up to 17 3/4 inches long. Banana slugs intertwine themselves in an S pattern, in which each one gives and receives sperm. However, un-twining themselves after mating is difficult, and could result in "apophallation" - one slug actually gnaws off the penis of the other (Gordon 1994: 31-32).

The two large snails are Missy and Biggie; the arrows are pointing to protruding dark spots, which are their penises at half-mast. The small snail towards the top is an innocent bystander, just trying to mind its own business.

Part of the pre-mating "dance", which is unique to only grove snails. The video is blurry, but since their dicks are out you probably get the point.

Of course I got a video of my snails’ pre-mating ritual – you know, for science – but I refrained from getting one of them in the act itself (I know they’re just invertebrates, but they still deserve to have at least a little goddamn privacy). As you can see in the photo and video, they both have taken out their penises and they began their “mating dance”, which actually lasted for three and a half hours. Their actual copulation took an additional three hours. For another version of the snail mating process, zefrank1 made a lighthearted video about it, which gets into the actual “spirited love darting” process. The gestation period for slugs and snails vary among each species. For grove snails, it’ll take approximately 3-4 weeks for a clutch of eggs to appear after mating. It usually takes an additional 4 weeks for those eggs to hatch, depending on environmental circumstances.

Useless (but hilarious) slug fact: slug genitals are disproportionally large, compared to the rest of their body. An example is that of the great grey garden slug - whose penis is half the length of its body. These traits are also reflected in their scientific names - for example, one banana slug species, dolichophallus, is Latin for "really long penis" (Gordon 1994: 31-32). Now you have a nice lunch-time conversation topic.

Though snail mating is fascinating, I could definitely live without seeing it in action ever again. Anyway, if you're interested in learning more about slugs and snails, I absolutely recommend these two books (Gordon 1994, 2010):