On Exhibit: Rocky Shore
diatoms and other plankton
less than 1 inch (2.5 cm) wide
hermit crabs, shore crabs and other crabs and shrimp; Order: Decapoda
several species from Alaska to Baja California
Tiny porcelain crabs live in abundance in Pacific Coast tide pools. They hide under stones, between mussels in mussel beds, among sponges and tucked into tufts of algae. Safely concealed, they eat by sweeping feathery arms through the water like fine-meshed nets to capture diatoms and other drifting plants and animals.
If its camouflage fails and a predator threatens, a porcelain crab can drop a claw or leg to distract the attacker and give itself a chance to scurry away. The crab lives to see another day, and the leg or claw grows back before long.
Rocky shore creatures are at risk from coastal development and pollution such as oil spills and agricultural runoff. And rocky shores aren't as rugged as they seem. Careless visitors can trample tide pool animals underfoot, and some collect crabs or other animals. These animals seldom survive being taken from their natural habitat.
A female porcelain crab less than an inch long may carry nearly 1,600 eggs at a time (though most carry only around 600). Up to 860 porcelain crabs have been found living in a 10-square-foot (one-square-meter) section of a mussel bed off Pacific Grove, California!