Arthropoda · arthropods

Blue crab

Callinectes sapidus

Portunidae · swimming crabsIUCN: Not evaluated
Blue crab
Photo: The Children's Museum of Indianapolis · CC BY-SA 3.0 · Wikimedia Commons · resized

A swimming crab with paddle-shaped back legs and the Chesapeake Bay's signature catch.

Fun factIts scientific name means 'beautiful savory swimmer.'

Waters
Northeast US, Northwest Atlantic, Tropical Atlantic & Caribbean
Depth zone
Coastal shallows & estuaries
Diet
Clams, fish & almost anything
Size
Carapace up to 23 cm

Classification

Arthropoda › Malacostraca › Decapoda › Portunidae

  1. Kingdom Animalia animals
    • Many-celled organisms that eat other living things for energy (heterotrophs)
    • Cells have no cell walls
    • Most can move at some stage of life
  2. Clade Bilateria bilateral animals
    • Body has a left and right side that mirror each other (bilateral symmetry)
    • Head end with concentrated nerves; three tissue layers
    • Includes about 99% of all living animal species
  3. Clade Protostomia protostomes
    • In the embryo, the first opening usually becomes the mouth
    • Main nerve cord runs along the belly (ventral)
    • Includes mollusks, worms, and arthropods
  4. Clade Ecdysozoa molting animals
    • Grow by shedding their outer layer (molting, ecdysis)
    • No cilia used for movement
    • Includes arthropods and nematode worms
  5. Phylum Arthropoda arthropods
    • Hard outer skeleton made of chitin (exoskeleton)
    • Jointed legs and a segmented body
    • The largest animal phylum by species count
  6. Subphylum Crustacea crustaceans
    • Two pairs of antennae
    • Branched (biramous) legs in many species
    • Most breathe with gills
  7. Class Malacostraca crabs, shrimp & kin
    • Body of a head, 8-segment thorax, and 6-segment abdomen
    • Includes crabs, shrimp, lobsters, krill, and isopods
  8. Order Decapoda ten-legged crustaceans
    • Ten walking legs, the first pair often with claws
    • Shell covers head and thorax together (carapace)
  9. Suborder Pleocyemata egg-brooding decapods
    • Females carry their eggs under the abdomen until they hatch
    • Includes true crabs, lobsters, and most shrimp
  10. Infraorder Brachyura true crabs
    • True crabs: abdomen tucked tightly under a broad carapace
    • Walk sideways on four pairs of legs
  11. Family Portunidae swimming crabs
    • Swimming crabs whose last legs are flattened into paddles
  12. Genus Callinectes
    • Species in the same genus are very close relatives and often look alike.
  13. Species Callinectes sapidus Blue crab

Closest relatives in the guide