Scylla (scientific name: Scylla) is a genus of Portunus, with 4 species. The head breastplate is oval, and its length is equal to or slightly less than 2/3 of its width. The back is rounded and has an "H" pattern; The surface is smooth, and the gastric heart groove is not obvious; The forehead has 4 teeth; The claws are thick; The inner edge of the wrist has sharp thorns, and the outer edge has or does not have 2 thorns.
The metacarpal joint has strong thorns at the edge of the wrist joint; There is a tuberous protrusion on the inner side next to the wrist joint; Seat nodes are not spiny; The second to fourth pairs of feet are similar, and the two ends of the fifth pair of feet are paddle-shaped; The male abdomen is divided into 5 sections, showing a wide triangle; The female abdomen has 7 segments and is broadly oval; The color of crustaceans varies with species and living environment.
As a burrowing aquatic crustacean, the blue crab likes to inhabit the muddy beaches, mangroves or marshes in the intertidal zone, burrow in caves during the day and come out for food at night. In summer, I like to use my feet to support my body in the high tide zone, and when it is low temperature, I lurk in the sand, only showing my eyes. In the natural environment, blue crabs mainly feed on small fish, shrimp, crabs and shellfish. Widely distributed in the Pacific Ocean and Indian Ocean.