''Panopeus herbstii'', also known as the black-fingered mud crab, black-clawed mud crab, Atlantic mud crab or sometimes common mud crab, is a species of true crab, belonging to the

infraorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classific ...

Brachyura, and is the largest of the mud crabs. ''Panopeus herbstii'' is small, growing to about 4 cm, with black-tipped

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or Arthro ...

s of unequal size. ''P. herbstii'' has a strong

exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...

, with very thick and strong claws. The shell is a dull gray and brown color. ''Panopeus herbstii'' is found along the Atlantic coast of North America, from

Boston, Massachusetts Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...

to Santa Catarina, Brazil and on

Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...

. It is the most common xanthid crab on the east coast of the United States. It is found on muddy bottoms, where it takes refuge under stones and shells or among

sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...

s and weeds, but it is rarely seen in the open. It feeds mainly on young

clam Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams h ...

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but no ...

s, and periwinkles; it cracks open their shells with its strong claws. Mud crabs are especially fond of

hermit crab Hermit crabs are anomuran Decapoda, decapod crustaceans of the superfamily (taxonomy), superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit c ...

s, which are grasped by the legs and pulled out of their protective shells. Like most mud crabs, it is a scavenger. Young ''P. herbstii'' are an important food source to other marine animals. It mainly eats oysters.

References

{{Portal bar, Crustaceans Xanthoidea Crabs of the Atlantic Ocean Crustaceans described in 1834 Taxa named by Henri Milne-Edwards