Perverted cannibalistic hermaphrodites haunt the Pacific Northwest!

This is a repost from my former blog The Oyster’s Garter and was originally published on March 24, 2008. I’m re-posting in honor of Kate Clancy‘s & Scicurious‘ Sex, gender and controversy: writing to educate, writing to titillate session at Science Online 2012, since this is one of the silliest bits of sex-related writing I’ve ever done. It is certainly much easier to be non-controversially ridiculous when writing about invertebrates.

Horrific sexual hijinks are taking place beneath the majestic redwoods of central California! I’m not talking about San Francisco – the Fulton Street Fair looks like a Bible Belt county fair compared to this. No, I speak of the unspeakable sexual habits of the lovely banana slug.

The banana slug, so called for its fetching yellow color with occasional black spots, is the second-largest slug in the world (and the mascot of UC Santa Cruz). For most of its life, it crawls about the Pacific redwood forest in the normal sluggy fashion, munching upon rotting leaves, mushrooms, animal droppings, and other detritus. But if a slug crosses the pheremone-soaked slime trail of a fellow slug, prolonged tantric slug-sex ensues…and ends in a most ghastly fashion.

Before we get to the juicy bits (slimy bits?), you need to know a bit about slug anatomy. Most slugs are simultaneous hermaphrodites and have both a penis and a genital opening, so that when they have sex they both fertilize and are fertilized. (They then both lay eggs somewhere damp and out of the way, and that is it for parental care.) Also, due to the vagaries of evolution, the genitalia and anus of slugs are located on the right side of their heads. This is because slugs are descended from snails with spiraling shells – the snails needed to move their naughty bits down in order to extend outside the shell, so they put them on their head. Even though slugs have since lost their shells, they have retained this feature of snail anatomy. So most gastropods actually poop on their own heads – ain’t nature grand?

So, slug-sex begins with head-waving and gentle biting of the other slug’s genital opening. Once they get to the Big Deed, the slugs both insert their penises into the other’s genital opening (remember, both are on the right side of their head) and go at it for hours and hours. And hours and hours and hours. And then…sometimes…one or both slugs will CHEW OFF THE OTHER’S PENIS. Yep, they rasp with their radula until the penis comes off. Then they slurp down the penis like spaghetti.

I bet your very first reaction was, “Boy, I sure hope there is a video of sexy slug cannibalism!” Of course there is, gentle reader! If you still want more, have some auto-apophallation (isn’t that a great bit of jargon?) – this is a video [warning: big file] of a slug chewing off its own penis.

Do not fear too much for the penis-less slug. While the penis does not grow back, the slug is not condemned to a lonely sexless life. It can still enjoy slug-sex as the receiving party. But perhaps the more educated banana slugs contemplate the theories of Freud and shake their tentacles in rage at the cruel hand of Fate. Or at least the cruel radula of their ex.

This post was inspired by the slugs in flagrante in the above photo, which I met near the Little Sur River this past weekend. (The openings you see are not their genitals, but their pneumatostome, which is how they breathe.) It is unknown if any penis-gnawing ensued, as the slugs were still making the sweet yin-yang of love amidst the flowers when I left.