The blue crab Callinectes ornatus
is a decapod crustacean in the Portunidae
family. It is a strong and agile swimmer powered by a pair of flat, oar shaped rear legs called swimmerets. Swimmerets allow C. ornatus
to rapidly swim backwards, sideways, and sometimes forward (Barnes 1980). The color of this species varies considerably. Adult males have a carapace that is uniformly olive to dark brown with a large orange spot posteriorly that can appear round to blotchy (Gore and Grizzle 1974, Gore 1977, Williams 1984). There are distinct ivory white tips on all the spines on the front of the carapace (Gore 1977). Juveniles are not as brilliantly colored appearing olive-yellow to greenish. The length and curvature of the reproductive organs (gonopods) are distinctive in mature males for each of the Callinectes
species (Gore 1977, Barnes 1980) See illustrations from Williams (1974) below.