Ever wander the beach, find the perfect shell, and flip it over only to find that there is a perfect little hole drilled into it? I've had it happen dozens of times. I always wondered what caused it, but for some reason assumed that the mystery holes formed postmortem.
Thanks to Jelo, the mystery of the shell holes is solved.
Enter the moon snail. These large snails cruise the sandy foam of the shoreline and tidal pools in search of their prey: clams, mussels, etc. If it's got a shell, it's food. They're like gastropod bulldozers with one mission in mind: a seafood dinner.
They look too big for their shells, don't they? That's because when they come across a less mobile clam, they envelop it with their over-sized mantle and go to work drilling their way through the shell while the clam lies there helpless. 
They do so with a raspy tongue (radula) that scrapes a perfect hole in the shell (aided by secreted chemicals). Once they've made their way through the shell, they proceed to dine. It's a slow process, but snails are patient (more snail wisdom to come in future posts). There are lots of ways to die in the ocean. This one seems like one of the less pleasant ones.
Think the snail won't fit inside the shell? Just pick one up and start poking it. It will shed water like a little sprinkler system until it fits inside. Go on. I dare you. Be sure to video it.
Thanks, Jelo. Now I know who the culprits are.
Jan 8, 2009
Mystery Holes
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8 comments:
Being part French, I feel a strange urge to cook this thing in garlic butter...
Yay moon snails! I love their bivalve-drilling ways.
Kinda interesting: predatory pressure is a determining factor as to where the snails drill. If there are many predators around that might find a tasty snack in that Moon snail's huge foot, the snails tend to drill towards the "lip" of the bivalve shell. It's faster (the shell is thinner there), so they can get their meal before they become the meal, but it's more dangerous. The prey may clamp down and damage the radula if the snail drills too close to the edge, or gets a cranky dinner.
Ain't Nature fun?
They make nifty egg cases too.
Oooo, thanks for this one, Wombie! I've always wondered what these beasties look like. When my parents moved to the shore, I outfitted them with new ceiling fan pulls by using shells with the handy predrilled holes. Thanks, moon snails!
Moonsnails, btw, are quite edible and very tasty.
If the snail drills while the bivalve is still alive, I don't think the hole is made "postmortem" maybe during mortem?
tmarisco -- I guess the term would be 'antemortem' technically....
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