Monday, June 08, 2015

Messy crab, with a hat.

Three weeks ago, wading in the eelgrass beds at the bottom of the tidal plain, I saw hundreds of egg masses, pink and yellow, and their parents, opalescent nudibranchs and bubble shells. A couple of days ago, the tide was even lower, and I spent two hours making figure-eights in the same area. And there were no pink and yellow eggs, no nudibranchs, few bubble shells.

Everything has its own season.

This week, the beds are full of blue anemones, sea stars, and crabs. Unusual crabs: crabs I'd never seen before.

For example, this little guy.

He's less than an inch across.

He is completely covered in algae or diatom fuzz, and is wearing a comparatively huge barnacle on his back. Good for camouflage; not so good for the purpose of identification.

The carapace is triangular, with a long cap protecting his head area. It's hard to tell if it's smooth or bumpy, but the edges are wavy, rather than toothed like the shore crabs' carapaces, or sharp, like the kelp crabs. His pincers are bluish*, with orange tips; the legs are also tipped with orange.

I've been examining the photos in the Encyclopedia with a lens, trying to find a match. The closest I can find is the sharpnose crab, Scyra acutifrons, which grows to just under 2 inches across. Adult males have long pincers, but the females are similar to this one. Or maybe he's a juvenile decorator crab, Loxorhynchus crispatus. These grow to about 5 inches across the carapace.

Both these crabs "decorate" their shells, adding algae, anemones, barnacles, diatoms, what have you. And in both species, the males have long pincers, while the females' pincers are about the length of the legs.

Here he is upside-down, and struggling to right himself. From here, he looks like a male, with the narrow plate on the abdomen.

Here's how I saw him at first, under a foot of water:

Under the water, the diatom fuzz is more apparent. His pincers are definitely blue. His eyes look blue, too.

Do you recognize this crab? Can you help with the ID?

*The blue coloring could also be because he is young, and his skin is semi-transparent, so the blue blood shows through.


  1. the ditom make it look like the legs have no joints

  2. Great camouflage for a small guy trying to survive in a place with larger, hungry critters. - Margy

  3. Upupaepops, yes, they do. I almost felt like scrubbing his back to get a better look at him, but as Margy said, the camouflage could save his life. Probably has already.


If your comment is on a post older than a week, it will be held for moderation. Sorry about that, but spammers seem to love old posts!

Also, I have word verification on, because I found out that not only do I get spam without it, but it gets passed on to anyone commenting in that thread. Not cool!