Species Description: 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.
Potentially Misidentified Species: It can be difficult to distinguish the juveniles, immature males, and adult females of C. ornatus from C. danae and C. similis (Williams 1984). C. ornatus is very similar to C. similis and the two were confused until the 1960's (Gore 1977).
C. similis can be distinguished from C. ornatus by the pale translucent blue dactyls of the swimming legs and the propodi that are olive on the ends and banded with translucent blue mesially.
Regional Occurrence: Callinectes ornatus is distributed from North Carolina to Rio Grande de Sul, Brazil (Williams 1984, Branco et. al. 2002) living at depths of up to 75 meters on sand and mud bottoms (Branco et al. 2002). The ornate blue crab is found in river mouths but more commonly occurs offshore (Negreiros-Fransozo et al. 1999). Juveniles are usually found in shallower habitats.
IRL Distribution: Adults and juvenile of the ornate blue crab are common in seagrass beds in the lagoon (Gore 1977).
Age, Size, Lifespan: Male Callinectes ornatus are usually slightly larger than the females, measuring up to 60 mm, while the female carapace can measure up to 58 mm (Williams 1984). It is unknown whether males and females have different mortality rates (Negreiros-Fransozo et al. 1999).
Abundance: The ornate blue crab is common in the Indian River Lagoon and shallow tropical habitats of warm waters in the eastern Atlantic oceans. In a population of Callinectes ornatus from Ubatuba in Brazil, the males made up 63% of the population, outnumbering the females 1.7 to 1 (Negreiros-Fransozo et al. 1999).
Reproduction: Records of museum collections of oviparous females suggest that Callinectes ornatus spawn year-round (Williams 1984). Adult females move offshore to find temperature and/or salinity conditions that are best for spawning. One female can mate with several males during the same reproductive period (Negreiros-Fransozo et al. 1999).
Embryology: In the Portunidae, there are generally 7 zoeal stages and 1 postlarval, or megalopal stage. Occasionally an eighth zoeal stage is observed. Larval release usually occurs at high tide assuring larval abundance is at its peak during the ebbing tide. Crab larvae are advected offshore, and complete development in the coastal shelf waters. The typical time for development through the 7 zoeal stages is between 30-50 days before metamorphosis to the megalopal stage. The megalop is capable of postponing metamorphosis to first crab and may persist from 6-58 days. It is widely believed that the megalopal stage subsequently returns to the estuaries for settlement, and recruitment to adult populations.
Temperature: Callinectes ornatus is usually found in tropical seas in temperatures ranging from 18-31°C (William 1984).
Salinity: Specimens have been trapped in fresh water but most collections of C. ornatus come from waters with higher salinities (William 1984). Laboratory experiments with portunid crabs in the genus Callinectes demonstrated that C. ornatus has lower tolerance to hyposaline conditions (reductions in salinity). Individuals of C. ornatus were shown to begin dying off when seawater was diluted by 25% (8.7 ppt) whereas C. sapidus, C. exasperatus, and C. danae tolerated extreme hyposaline conditions of 3.5 ppt (Norse 1978).
Trophic Mode: Callinectes ornatus is both a saprophagous species, feeding on decaying matter, as well as an active predator. C. ornatus will dig into the substratum in search of food, feeding on mollusks, especially bivalves, and other crustaceans, including brachyura (true crabs), other species of Callinectes, algae, polychaetes, echinoderms, and foraminifera (Branco et al. 2002).
Competitors: Competitors of the ornate blue crab are other crustaceans, in particular C. sapidus and C. similis.
Special Status: Because Callinectes ornatus occupies the same habitats as the commercial species, C. sapidus, it is impacted by the crab fishery along western Atlantic coast. In the Ubatuba region of Brazil it is a major fishery (Negreiros-Fransozo et al. 1999).
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