We covered the twisted, beautiful sex lives of slugs in our Valentine's Day episode last year. I even made you some lovely cards. But now science has revealed a new position for the amorous gastropods: cephalo-traumatic secretion transfer.
Yes, as reveled in Proceedings of the Royal Society B, the sea slug Siphopteron inserts its penis directly through its hermaphroditic partner's forehead.
I'll let that sink in -- the mental image, not the slug penis itself.
The Guardian does a good (though perhaps overly cheeky) job of walking us through this mind-rending form of copulation right here, but I'll try to break it down via captions to the image above.
(A) Here we see Siphopteron's sinister-looking everted, bipartite penis.
(B) Here we see "reciprocal copulation with both penile stylets inserted into the mating partners' foreheads."
(C) Here's a close-up photograph! The penile stylet of the left-hand slug is inserted into the forehead of the right-hand slug.
(D) Here wee see it all drawn out in three illustrations. Absolutely lovely.
So if you've ever woken up with a penis drawn on your forehead in magic marker, look on the bright side: It could have been much worse.
Thanks to Lauren over at TechStuff for bringing this one to our attention!