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Commercial Importance Unlike vertebrates whose skeletons grow with them, most invertebrates must molt or “shed” their outer layer (exoskeleton) in order to grow larger; blue crabs are no exception to this rule. This molting is called “ecdysis.” Ecdysis happens in three stages: precdysis, ecdysis, and postecdysis. Precdysis begins with a release of hormones under their outer, hard shell. This shell is attached to the crab with connective tissues that separate and allow a new shell to grow underneath. Ecdysis begins when the crab generally stops eating. The crab will then “take in” water and crack the old shell at a specific weak point. For the blue crab, this weak area is along the back of the shell. The crab is now able to “back out” of the old shell. The crab then rapidly suctions in water to swell its body to a size about 33 percent larger than the old shell. The old shell remains empty, but completely intact. After molting, these crabs are referred to as “soft shell crabs.” Postecdysis is defined when the shell begins to harden. Often the crab will consume its molted shell in order to obtain extra calcium. The blue crab is one of the five most commercially harvested species in the Gulf of Mexico. Blue crabs were commercially harvested as long ago as 1880. Records indicate there were only two Gulf Coast states to take part in this harvesting: Louisiana and Texas. In 1880 alone, an approximate 324,000 pounds of blue crabs were harvested valued at approximately $8,000. By 1950, all five Gulf States had begun to commercially harvest blue crabs; the states landed approximately 18,816,000 pounds. Between 2007 and 2009, an average of 55 million pounds of blue crabs were harvested by the Gulf states. These 55 million pounds were sold for an average of 43 million dollars. During these years, the blue mediagalley.usatoday.com crab was ranked number four in the top five commercial species by poundage and number five by monetary value. Many commercial blue crabbers today use crab traps (or crab pots) to facilitate their catch. pbs.org Ecdysis (Molting) This brochure is funded with qualified outer continental shelf oil and gas revenues by the Coastal Impact Assistance Program, United States Fish and Wildlife Service, U.S. Department of the Interior through a grant award to the Mississippi Department of Marine Resources. Blue Crab Distribution Blue crabs are natively found along the Atlantic coast of the western hemisphere. They are found from Canada, throughout the Gulf of Mexico and around the curve of Brazil in South America. The blue crab range is highlighted on the map below. Blue Crab Callinectes sapidus Remember The Institute for Marine Mammal Studies (IMMS) is a non-profit organization established in 1984 for the purposes of public education, conservation, and research of marine mammals and sea turtles in the wild and under human care. Located in Gulfport, MS, IMMS has been an active participant of the National Stranding Network since its inception. IMMS is a premiere organization in the Mississippi-LouisianaAlabama sub-region of the Gulf Coast with the capability and expertise to care for sick and injured marine mammals and sea turtles Additionally, IMMS promotes public awareness of marine conservation issues through its involvement in the community. animals.nationalgeographic.com Prepared by Melissa Welsh, 2012 While blue crabs are predators, they are also prey for a variety of animals, such as: Sea bass, flounders, sharks, and catfishes River otters and raccoons Alligators and sea turtles Institute for Marine Mammal Studies P.O. Box 207 Gulfport, MS 39502 Phone:228.896.9182 Fax: 228.896.9183 Email: [email protected] Website: www.IMMS.org The Institute for Marine Mammal Studies Reproduction Phylum: Arthropoda Sub-phylum: Crustacea bluecrab.info Class: Malacostraca Order: Decapoda Family: Portunidae Genus: Callinectes Species: sapidus aqua.org General Information Blue crabs also have the ability to regenerate legs. If a predator has a hold of one leg or claw, the crab is able to selectively release the appendage and swim away. This leg will regrow throughout several molts. “Sally” “Jimmy” In general, it is easy to distinguish between male and female crabs by viewing their “apron” or underside. Male crabs possess a shape resembling the Washington Monument or an inverted “T.” Immature females have a triangular shape on their aprons, while the mature females’ aprons are more circular in shape. Male crabs are often referred to as bluecrab.info “Jimmy” and female crabs are known as “Sally” or “Sook” depending on her maturity. A sook is a fully mature female crab. “Sook” tpwd.state.tx.us Atlantic blue crabs, or simply “blue crabs,” are given their name not from the color of their shell, but rather the blue colored tips of the male’s claws. The blue crab’s scientific name (Callinectes sapidus) is derived from the Greek and Latin languages, respectively. This name literally translates to “beautiful, savory swimmer.” These crabs are benthic (bottom) dwelling animals. Blue crabs are typically carnivorous (meat/flesh-eating). Their preferred diet includes small fish, bivalves, and even other crustaceans. It is not uncommon, however, for a blue crab to eat plants or detritus (dead and decaying plant and animal matter). Throughout their lives, blue crabs travel and live within a wide range of salinities (salt concentration). Generally remaining in a low salinity waters, female blue crabs often migrate to higher salinity estuaries and bays to hatch their eggs. A blue crab’s average life span in the wild is three to four years. Blue crabs have 10 legs: two claws (chilipeds), six walking legs, and two swimming legs. When grouped together, all of these legs are referred to as “pereopods.” References: Coulombe, D. A. (1991). The Seaside Naturalist: A Guide to Study at the Seashore. (pp. 128, 139-140). New York: Fireside. Guillory, V.; Perry, H.; Steele, P.; & Wagner, T.; Keithly, W.; Pelligrin, B.; Petterson, J; Floyd, T.; Buckson, B.; Hartman, L; Holder, E.; & Moss, C. (2001). The Blue Crab Fishery of the Gulf of Mexico, United States: A Regional Management Plan. Ocean Springs, MS: Gulf States Marine Fisheries Commission. Upon hatching, the young crabs are in a larval form. The crab in this larval stage is known as a “zoea.” At this point, the zoeae look nothing like a crab. Many different species of crabs’ zoeae resemble one another. While in this phase, the zoeae are considered “meroplanktonic” which refers to an organism that spends a portion of its life as plankton (microscopic organisms floating in ncsu.edu the ocean). A blue crab zoea may molt five to seven times before entering their second stage of life. This final molting occurs anywhere from 30 to 50 days after hatching. The second stage of a blue crab’s life if referred to as the megalopal stage. The young crab has come a long way from where it started as a zoea and begins to resemble a crab. The megalopa exhibits signs of 10 appendages (pereopods). On average, the megalopal stage is completed no longer than 20 days after entering this stage. dnr.state.md.us Kingdom: Animalia Life Stages bcsp.org Anatomy Scientific Classification When a female blue crab reaches maturity, she releases pheromones (chemical-like hormones) into the water. The males are attracted to these pheromones and approach the female. Once the male arrives, he embraces the female and holds her under him to protect her. He holds her using his first pair of walking legs. While she is offered protection, the female molts her exoskeleton for the last time; this molt is known as a maternal or terminal molt. It is only following this molt that the sook is able to mate. The male possesses two gonopods (“reproductive foot” or penises) which transfer packets of sperm (spermatophore) to the storage receptacles of the female (spermathecae). These spermatophores are stored until the female is ready to spawn. This may happen anywhere from two to nine months after mating. While she may only mate once in her life, a sook is capable of spawning several times. After mating, she begins to form an egg sac on her abdomen. Because this sac resembles a sponge, a pregnant sook is affectionately referred to as a “sponge crab” or a “berried crab.” The average female proOcean Expo Summer Camp 2011, duces approximately IMMS two million eggs in each sponge. Incubation time for these eggs varies in relationship to the environment. The average gestation is between one and two weeks. After this time, the young hatch and begin life on their own. . Following the megalopal stage, the crab molts once more and is classified as a juvenile. The crab continues to molt until it becomes an adult. Hill, J.; Fowler, D. L.; Van Den Avyle, M. J. (1989). Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Mid-Atlantic)—Blue Crab. U.S. Fish and Wildlife Service. Biological Report 82 (11.100). U.S. Army Corp of Engineers, TR EL-82-4. National Ocean Service, NOAA. 2011. The Gulf of Mexico at a Glance: A Second Glance. Washington, DC: U.S. Department of Commerce. www.animals.nationalgeographic.com/animals/invertebrates/ blue-crab/ www.bluecrab.info