Sunday, February 01, 2015

Why I left trash on the beach

In an expanse of clean sand, a crushed plastic gallon bottle spoiled the view. I picked it up, planning to remove it to the appropriate trash can, and found that it was being used as a roof by a mud shrimp.

Blue mud shrimp, Upogebia pugettensis, about 3 inches long

These crustaceans usually live in burrows about a metre deep; it is rare to find one on the surface. Apparently, if an adult is removed from his burrow, he can't dig a new one, so this exile may have become fish food as soon as the tide came in. At least the gallon jug kept the gulls from finding her*.

When I exposed her to the sunlight, she started crawling away. She's not very good at it on the surface; she kept unrolling her abdomen to push forward, but there was no purchase on the sand, and her legs didn't seem strong enough to carry her weight out of water. I took a few photos and dug her a new pool to crawl into. When she got there, I replaced her roof above her. Recycling takes several forms.

A couple of years ago, we found a Bay ghost shrimp in this same area:

Bay ghost shrimp, Neotrypaea californiensis

At first glance, these look very much alike, but the Bay ghost shrimp is pinker, more translucent, has no rostrum (the "hat" over the head area), and the pincers are more unequal in size.

The Blue has a hairy rostrum with a sharp point, rather difficult to see because of the hairiness. The legs and claws are hairy; you can see signs in the photo at the front bend of the large pincer. The colour varies from muddy brown to bluish. This one, in the slanting light of a late afternoon sun looked more orange; the blue shows up faintly in the legs.

(Compare; Google images of Urogebia pugettensis.)

*"Her": randomly-selected sex, because I don't like calling conscious beings "it". In these Blues, as opposed to the Bay ghost shrimp, males and females look alike at first glance.

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