Sunday, March 2, 2008

right-handed snakes

A paper that was published last year, that gives a wonderful example co-evolution. I'm not sure if it got much coverage (but may well be mistaken), but it really is great.

Snails often have clockwise shells (which in itself, is a wonderful example of the evolution of asymmetry). The authors show that snakes that prey on these snails have evolved to have more teeth on their right mandible than there left mandible. The authors also show that these snakes have a lot easier time eating snails with clockwise shells, than those with anti-clockwise shells. I remember seeing a video of this at a conference I was attending, and thinking at the time that it was the coolest thing ever.

The mutation in snails, which causes them to flip the spiral of their shells is thought to be one of the only clear case of speciation caused by a single locus, as left-handed snails have a lot of trouble mating with right-handed snails (see here). But why do left-handed snails arise and spread if they can not breed with the right-handed snails? Perhaps predation by right-handed predators offers a mechanism that would favor the left-handed snail species.

Masaki Hoso, Takahiro Asami, Michio Hori. Right-handed snakes: convergent evolution of asymmetry for functional specialization. Biology Letters. 2007
Davison A, Chiba S, Barton NH, Clarke B. Speciation and gene flow between snails of opposite chirality. PLoS Biology 2005.

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