Introduction to Oceanography: Biotic

About the Species

The common spider crab, also called the portly spider crab, is native to the Atlantic coast of North America. They inhabit all bottom types from Nova Scotia to southern Florida and the Gulf of Mexico. They are most common along bays and estuaries in coastal waters to the continental shelf.  They have long legs and walk along the substrate, foraging as omnivorous scavengers. They have poor eyesight; but, do have sensing organs on the end of each walking leg. Allowing them to identify food in the water or in the mud as they walk over it.  They use their long, thin claws to pick up morsels of detritus and algae, or to pull off food from a carcase.

This species exhibits sexual dimorphism, with males growing much larger than females, and having longer claws.  The females stop molting after they become sexually mature and remain the same size for the rest of their lives.  They overwinter in deeper waters off the coast and return to nearshore water in the spring.  Then, they aggregate in large groups for mating, and will spend the summer feeding in the eutrophic waters near estuaries and bays.  For more information, visit the species profile at the Chesapeake Bay Program’s website here.