English: Callinectes sapidus Rathbun, 1896 - oblique anterior view of a female blue crab in Florida, USA. (December 2013)

The crustaceans are a large group of arthropods that inhabit marine, marginal marine, freshwater, and terrestrial habitats. The crustaceans include crabs, lobsters, shrimp, crayfish, barnacles, ostracods, and other organisms. The oldest fossil crustaceans are in the Cambrian. The group experienced a significant radiation in the oceans during the Mesozoic Marine Revolution.

The above photo depicts a ~freshly dead female blue crab, Callinectes sapidus.

Info. from Witherington & Witherington (2007): "Blue crabs are swimming crabs in the Family Portunidae. Blue crabs have pointed projections on the sides of their carapace and swimming paddles on their hind legs. They are greenish and blue. Females have orange highlights and clawtips, and are more commonly beached than males. Female blue crabs are occasionally beached after migrating from estuaries to spawn at sea. Blue crabs are swift predators that eat mollusks, fishes, and other crabs."

Classification: Animalia, Arthropoda, Crustacea, Malacostraca, Decapoda, Brachyura, Portunidae

Locality: marine beach near the southern end of the Gulf of Mexico shoreline of Cayo Costa Island, southwestern Florida, USA

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More info. at: en.wikipedia.org/wiki/Crustacean and en.wikipedia.org/wiki/Callinectes_sapidus

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Reference cited:

Witherington & Witherington (2007) - Florida's Living Beaches, a Guide for the Curious Beachcomber. Sarasota, Florida. Pineapple Press, Inc. 326 pp.