|
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.
Comparative detail of the reproductive structures of mature male Callinectes. Modified from Williams 1974.
II. HABITAT AND DISTRIBUTION
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).
III. LIFE HISTORY AND POPULATION BIOLOGY
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.
IV. PHYSICAL TOLERANCES
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).
V. COMMUNITY ECOLOGY
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.
VI. SPECIAL STATUS
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).
VII.
REFERENCES
Barnes RD. 1980. Invertebrate Zoology. Saunders College/Holt, Rinehart and Winston, Philadelphia, PA. 725 p.
Branco JO, Lunardon-Branco MJ, Verani JR, Schveitzer R, F. Souto FX, and WG
Vale. 2002. Natural diets of Callinectes ornatus Ordway, 1963
(Decapoda, Portunidae) in the Itapocoroy inlet, Pehna, SC, Brazil. Braz. Arch.
Biological Technology 45:35-40
Gore RH. 1977. Studies on decapod crustaceans from the Indian River region
of Florida. VII. A field character for the rapid identification of the
swimming crabs Callinectes ornatus Ordway, 1963 and C. similis Williams, 1966
(Brachyura: Portunidae). Northeast Gulf Science 1:119-123.
Gore RH and RE Grizzle. 1974. Studies of the decapod crustacean from the
Indian River Lagoon region of Florida. III. Callinectes bocourti A. Milne
Edwars, 1979 (Decapoda, Portunidae) from the central east coast of Florida.
Crustaceana 27:306-308.
Negreiros-Fransozo ML, Mantelatto FLM, and A Fransozo. 1999. Population biology
of Callinectes ornatus Ordway, 1863 (Decapoda, Portunidae) from Ubatuba (SP),
Brazil. Scientia Marina 63:157-163.
Norse EA. 1978. An experimental gradient analysis: hyposalinity as an
"upstress" distributional determinant for Caribbean portunid crabs. Biological
Bulletin 155:586-598.
SCDNR. Undated. Blue Crabs of the South Atlantic Bight. Adobe pdf document available online.
Williams AB. 1974. The swimming crabs of the genus Callinectes (Decapoda:
Portunidae). Fishery Bulletin 72:685-798.
Williams AB. 1984. Shrimps, Lobsters, and Crabs of the Atlantic Coast of the Eastern United States, Maine to Florida. Smithsonian Institution Press,
Washington DC. 550 p.
Report by:
Melany P. Puglisi, Smithsonian Marine Station
Submit additional information, photos or comments
to:
irl_webmaster@si.edu
Page last updated: August 1, 2008 |
