Friday, April 15, 2011

Discarded finery

Scattered all along the upper levels of Crescent Beach this week, we saw dozens of these crab carapaces:

Helmet crab shell, in shallow water. About 2 inches tip to tip. They may grow to 4 inches.

At first, I thought there had been a die-off, and then I looked more closely. Each one was just the clean upper carapace, unbroken, with no legs or "innards" attached. So it was a general molt, which signals mating time. The crabs come up to the intertidal zone, and the males choose their mate and hold onto her until she molts. Females are not able to mate until they have a new, still soft, carapace.  Within a day or so, the shell has hardened, and the opportunity gone for this year.

We don't usually find these crabs (Cancer cheiragonus) live in the intertidal zone, so this is all the evidence of crabby romance that we will see.

A small collection of sun-dried shells, inside a larger Dungeness crab shell.

I love the textures of these crab shells, especially the pale yellow inner wall of the helmet crab on top. The shell of the Dungeness is quite different, sort of like a stuccoed wall. Click on the photo to see these full size.


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