Malacology morning

My wife thought this story about left-handed snails having a competitive advantage, in that they seem to be better able to escape predation by right-handed crabs, was pretty cool. She also recalled that I'd scribbled up something about snail handedness before, so to jump on the bandwagon, I've brought those stories over from the old site.

The handedness of snail shells is a consequence of early spiral cleavages in the blastula. It's a classic old story in developmental biology—everyone ought to know it!

There was also a story last year about shell chirality in Euhadra. There, it wasn't a matter of predation, but a potential isolating mechanism, and one where mating compatibility and character displacement could play a role.

Everyone can read up on snails while I'm off at class this morning.

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How come left-handed snails are so rare? Lightning Whelks seem to be about the only left-handed snails here in FL, and if you find a shell from some other species that is left-handed, it's considered very valuable.

This is probably a dumb question, but wouldn't scars on right-handed snails indicate that they *survived* an attack? Making right-shelledness a good thing? Maybe left-handed snails get, y'know, swallowed whole or something. Or does "scarring" in this context not imply "healing and living to trail goo another day?"

The snails in our aquarium are a lot bigger than the crabs, so I can't effectively test this out at home, but I'm all curious now.

I seem to remember an interesting characteristic in the way the handedness is transmitted : something about the maternal RNAs being important, so that the right/left handedness of a snail is determined by the genotype of the mother for the particular gene.
No reference to give, though.