Left-handed Snails Beat Snail-eating Snakes

Masaki Hoso reported that the snail-eating snake, Pareas iwasakii, has lopsided jaws to better enable it to tug snails out of their shells. Most snails have shells that whirl clockwise (to the right) so P. iwasakii has evolved an upper jaw with more teeth on the right side than the left. In a sample of 28 snakes, the Hoso found each one had an average of 17.5 teeth on its left jaw and 24.9 teeth on the right.
The lack of symmetry helps the snake pry the snails out of their shells with alternate retractions of their left and right jaws, a technique called "mandible walking".

Here's a video of the snake preying upon a "right-handed" snail.

The snail, Satsuma c. caliginosa, has countered the snake's adaptation by evolving a left-handed swirling pattern.

Hoso et al. write in Biology Letters:

In addition, our experiments demonstrate a defensive function of sinistrality for snails against snake predators. Sinistral variants have been generally considered to suffer selective disadvantages on account of the overwhelming predominance of dextrals (Vermeij 1975, 2002; Johnson 1982; Gould et al. 1985; Asami et al. 1998; but see Dietl & Hendricks 2006). However, sinistrals should enjoy a selective advantage over dextrals under chirally biased predation by snakes. The remarkable diversity of sinistral snails in Southeast Asia (Vermeij 1975; Hoso et al. 2006, unpublished data) may be attributable to ‘right-handed predation’ by the snakes.

In the video below, P. iwasakii attacks but fails to consume the lefty snail.

How cool is that?

Hoso, M., Asami, T., & Hori, M. (2007). Right-handed snakes: convergent evolution of asymmetry for functional specialization Biology Letters, 3 (2), 169-172 DOI: 10.1098/rsbl.2006.0600

Evolution 2009 Moscow, ID

I have finally arrived in Moscow, ID for the the joint annual meeting of the Society for the Study of Evolution (SSE), the Society of Systematic Biologists (SSB), and the American Society of Naturalists (ASN). It was a long and enjoyable drive from Salt Lake City where I met up with Weber State evolutionary biologist and fellow blogger Jon Marshall. Along the way we stopped at Waterfall Canyon and the Hot Pots in Ogden, the Craters of the Moon, Ernest Hemingway's grave, and more hot springs in Stanley.

Several other bloggers are participating in the festivities.

I'll be posting about the scientific content as time permits over the weekend, but now it's time for a few beers at the opening reception and Genie Scott's Stephen Jay Gould Award Lecture "The Public Understanding of Evolution and the KISS Principle."

Roald Dahl on Vaccines

When I was younger, my favorite book was James and the Giant Peach by Roald Dahl (also author of Charlie and the Chocolate Factory and Matilda). Turns out that book was dedicated to his daughter Olivia, who tragically died of measles. In this article, Dahl stresses the importance of vaccinations.

Dahl writes "...there is today something that parents can do to make sure that this sort of tragedy does not happen to a child of theirs. They can insist that their child is immunised against measles. I was unable to do that for Olivia in 1962 because in those days a reliable measles vaccine had not been discovered. Today a good and safe vaccine is available to every family and all you have to do is to ask your doctor to administer it. It is not yet generally accepted that measles can be a dangerous illness. Believe me, it is. In my opinion parents who now refuse to have their children immunised are putting the lives of those children at risk.... It really is almost a crime to allow your child to go unimmunised."