May 27 - Pinnotheres pisum

Some crabs, like hermit crabs, live in the discarded shells of mollusks, but some, like the pea crab Pinnotheres pisum, just can't wait for the resident to move out first and move in as a roommate -- but the kind of bad roommate that steals your food and damages your house. P. pisum, which is at most about half and inch wide, lives in the mantle cavities of bivalves such as mussels and clams where it picks the food off their gills and can severely damage them in the process (kind of like you might imagine if something with 10 legs lived in your fridge full-time.) I chose this photo from wikipedia (click on it for a blown-up view), which shows a pea crab that has fallen out of the clam that an otter is eating. Better go find another landlord, little crab!