"Single gene creates snake-resistant mirror-image snails, and maybe some new species"

Definitely my new favourite science headline, courtesy of Discover magazine and coming via @David_Dobbs on Twitter.

You can click the link to view the whole article, but in summary:

1. Japanese Satsuma snails (yes, really, and I haven't even been saving up this story especially for Christmas) have shells which mostly spiral in a clockwise direction, and sit slightly on the snail's right hand side.  A small number of snails have anti-clockwise shells, which sit slightly to the left; a single gene determines which type of shell the snail will get.

2. Snails can only mate with other snails whose shells spiral in the same direction.  They're not being fussy, it's just physically impossible for them to do otherwise. (I am imagining all sorts of Romeo and Juliet type scenarios where poor, love-struck snail couples are tragically torn apart becuase the cruel, cruel hand of fate has bestowed the wrong kind of shell on one of them.)

3. Snail-eating snakes are designed to eat the snails whose shells spiral clockwise.  They stalk their prey from the left, giving them clear access to the side of the snail which is less protected by shell.  Then they use the backward pointing fangs of their bottom jaws to twist the snails out of their shells; there are more of these fangs on the right side of their jaws than on the left.

 4. All this means that if you're a  left-handed (anti-clockwise) snail, you'll be scraping the barrel when it comes to chooing a partner, but on the bright side you probably won't get eaten by a snake.  Not a bad trade-off in my book, but then as a left-hander I'm maybe a little biased.