They amble along, scraping away at their green dinners, unmolested under their domed roofs, ignoring the world around them. If I come across one moving and touch it gently, it immediately clamps itself down to the rock, and becomes immovable. Crabs pick at their shells hopelessly then; they can't break through.
But occasionally, a crab is fast enough to grab an edge before it is sealed to the rock, and tough enough to pry it up. The limpet tumbles to the floor beneath, and becomes dinner on the half-shell.
It's rare that a limpet survives the meal. But this one did.
|And here he is, broken shell, torn mantle, and all, peacefully eating algae on the glass.|
I don't know how he managed it: any time I've seen a dropped limpet, it was toast.