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Black-Fingered Mud Crab

Panopeus herbstii

Black-fingered mud crabs use their strong claws to crack the shells of clams, crustaceans and marsh periwinkles. (E. Guy Stephens/Flickr)
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Black-fingered mud crabs use their strong claws to crack the shells of clams, crustaceans and marsh periwinkles. (E. Guy Stephens/Flickr)

Also known as the Atlantic mud crab, the black-fingered mud crab is muddy brown in color with stout, black-tipped claws. It can be found on oyster reefs and along the muddy bottoms of marshes.

Appearance:

  • Muddy brown in color
  • Stout, black-tipped claws are unequal in size
  • A large tooth on the finger of its larger claw is visible when the claw is clamped shut
  • Four pairs of walking legs are hairy and slender
  • Grows to reach three-quarters of an inch wide and one and a half inches long

Habitat:

  • Prefers moderately brackish waters
  • Lives on oyster reefs and along the muddy bottoms of marshes
  • Can often be found under stones and shells or among masses of sponges and seaweed. Also finds protection inside bottles, cans and other trash

Range:

  • Found along the East Coast from Massachusetts to Brazil and on the island of Bermuda

Feeding:

  • Uses strong claws to crack the shells of oysters, barnacles and marsh periwinkles
  • Can also be found feeding on worms, fish and other crabs

Predators:

  • Predators include birds, fish and large crustaceans

Reproduction and Life Cycle:

  • Reaches sexual maturity between 18 and 24 months of age
  • Females carry fertilized eggs on abdomen until they hatch
  • Larvae hatch with undeveloped limbs and float through the water like plankton
  • Larvae molt four times over the course of 12 to 15 days before developing fully functional claws. A few weeks later, the so-called “megalopa” will settle into the sea floor and molt into a juvenile crab

Other Facts:

  • The black-fingered mud crab is the largest of five species of mud crabs found in the Chesapeake Bay. Other species include: the white-fingered mud crab, the flat mud crab, the equal-clawed mud crab and the grooved-wristed mud crab.

Sources and Additional Information:

  • Life in the Chesapeake Bay by Alice Jane Lippson and Robert L. Lippson
  • Atlantic Mud Crab -  Smithsonian Marine Station at Fort Pierce
  • Black-Fingered Mud Crab - The Uncommon Guide to Common Life on Narragansett Bay



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