Graceful crab (cancer gracilis)
Fooled you! Thought it was a juvenile Dungeness crab, didn’t you? Well, a lot of folks are fooled by this small relative that is only half the width of its bigger cousin at maturity. The graceful crab can be identified by several features: white-tipped margins of the shell teeth, maximum width of the shell at the next-to-last shell tooth (rather than the last tooth for the Dungeness), relatively smooth shell and bright purple on the legs.
Crabs have well-developed sense organs. The eyes are the two rounded projections at the front of the shell. Between the eyes are two tiny antennae that sense odors in the water.
They feed on a variety of food items including small clams, oysters and barnacles. Larvae and small juveniles of this species have been found on fried-egg jellys (see May 28, 2007, article), where they feed on other hitchhikers. They apparently also use the swimming jelly like a marine bus, letting the jelly do the traveling and then hopping off when it reaches shallow water.
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Normally occurring in sandy mud subtidal areas and occasionally in eel grass beds, they are commonly seen at low tide around the Boston Harbor Marina floats. They range from Alaska to northern Mexico, where they can be found from shallow water to a depth of about 400 feet.
David W. Jamison is a Boston Harbor resident and marine biologist.