Callinectes sapidusblue crab

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Geographic Range

Although the natural range of Callinectes sapidus spreads from the western Atlantic Ocean from Nova Scotia to Argentina, it was introduced, accidentally or deliberately, into both Asia and Europe. It has also been introduced into Hawaii and Japan. Callinectes sapidus is mostly found from Cape Cod (Massachussets) to Uruguay, but is also found north to at least Massachusetts Bay. (Hill, 2004; Shapiro, 2011)

Habitat

Callinectes sapidus, the blue crab, is a bottom-dweller found in a variety of habitats ranging from the saltiest water of the gulf to almost fresh water of the back bays. Especially common in estuaries, this species ranges into fresh water, and may be found offshore. The blue crab's habitat ranges from the low tide line to waters 120 feet (36 m) deep. Females remain in higher salinity portions of an estuary system, especially for egg laying. During times of the year when temperatures are colder, C. sapidus tends to migrate to deeper water. (Shapiro, 2011; Texas Parks and Wildlife, 2009)

  • Range depth
    1 to 36 m
    3.28 to 118.11 ft

Physical Description

Callinectes sapidus is easily identified by its body color which is generally a bright blue along the frontal area, especially along the chelipeds (the appendages bearing a "chela" or pincher-like claw). The remainder of the body is shaded an olive brown color. To accommodate swimming, the fifth leg is adapted to a paddle-like shape, as is the same with other portunids. Females have broad triangular or rounded aprons and red fingers on the chelae, whereas in the male the abdominal flap, or apron, is shaped like an inverted "T". Callinectes sapidus can grow to 25 cm in carapace length (CL), with carapace width being approximately twice the length. Growth is rapid during the first summer, with crabs growing from 70-100 mm CL. By the second year, maturity is reached at carapace lengths of 120-170 mm. Callinectes sapidus grows to adult size after 18 to 20 molts. (Hill, 2004; Steele, 1979; Texas Parks and Wildlife, 2009)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • male more colorful
  • Range length
    120 to 170 mm
    4.72 to 6.69 in

Development

Callinectes sapidus usually goes through seven zoeal stages and 1 postlarval, or megalopal stage. Sometimes an eighth zoeal stage is observed. Larval abundance is greatest when the tide begins to recede, because the larval release often occurs at the peak of high tide. Blue crab larvae are advected offshore, completing development in coastal shelf waters. Typical development through the seven zoeal stages is between thirty and fifty days before metamorphosis to the megalopal stage. The megalopa persists between six and fifty-eight days. The megalopal stage returns to estuaries for settlement, and eventual recruitment to adult populations. (Hill, 2004; Texas Parks and Wildlife, 2009)

Reproduction

Spawning peaks in Callinectes sapidus are closely associated with the region they inhabit. Unlike males, female C. sapidus mate only once in their lifetime, after the pubertal or terminal molt. When approaching this final molt, females attract males by releasing a pheromone in their urine. Male crabs compete for females and until molting occurs they will protect them. At this time mating occurs, and may last as long as 5-12 hours. (Hill, 2004)

Callinectes sapidus is highly fertile, with females producing from 2 - 8 million eggs per spawn. When females are in their soft-shell stage immediately after molting, the males transfer their sperm to them for storage. The male then protects the female until her new shell hardens. The females will spawn two to nine months after mating, laying up to eight million eggs. Spawning season is from December to October, with a peak both in spring and summer. When females are ready to spawn, they fertilize the eggs with the stored sperm and place them on the tiny hairs of the appendages on their abdomen. The female is called a "sponge" or "berry" crab while she carries eggs like this. The blue crab's incubation time is 14-17 days, which is when the eggs are brooded. During this time females migrate to the mouths of estuaries so that larvae may be released into high salinity waters. Blue crab larvae have a salinity requirement of at least 20 ppt, and show poor survival below this threshold. The megalops (or larvae) pass through eight stages in about two months before they begin to resemble adult crabs. Usually only one or two crabs survive to become adults, and they have a lifespan up to three years. (Hill, 2004; Texas Parks and Wildlife, 2009)

  • Breeding interval
    Males mate more than once, during each mating season, where females only mate once in their lifetime.
  • Breeding season
    All year, but spawning occurs mostly during the months of December until October.
  • Range number of offspring
    2 million to 8 million
  • Average number of offspring
    1
  • Range gestation period
    14 to 17 days
  • Average time to independence
    2 months
  • Range age at sexual or reproductive maturity (female)
    12 to 18 months
  • Range age at sexual or reproductive maturity (male)
    12 to 18 months

Males tend to stay and protect the female until she has grown her hard shell after molting, but males have no interaction with the young. The female will protect the young while they hatch, but do not have a significant role in parenting. This is because there are so many eggs, and the maturing time is much too long for her to watch over them. They have to be independent from the time they hatch, which is why most of them will die before they reach the adult age. (Hill, 2004)

  • Parental Investment
  • pre-fertilization
    • protecting
      • male
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

Callinectes sapidus has an average life span of 1-2 years. Many are harvested by humans before they would die naturally. In the St. Johns River, some blue crabs survive to four years of age. (Steele, 1979; Zinski, 2006)

  • Range lifespan
    Status: wild
    1 to 4 years
  • Average lifespan
    Status: wild
    2 years
  • Typical lifespan
    Status: wild
    1 to 2 years

Behavior

Callinectes sapidus is very aggressive when threatened, except when it has recently molted and still has soft shells leaving it vulnerable. The crab will also burrow into the sand to hide. Callinectes sapidus is an active swimmer and has its last pair of walking legs adapted to be shaped like a paddle to accommodate swimming. It also has three pairs of walking legs, and a powerful set of chelae. Since C. sapidus is highly mobile, the total distance traveled per day is about 215 meters. This species tends to be more active during the day than in the evening. The blue crab moves from zero to 140 meters per hour, with an average of 15.5 meters per hour. Crabs in general can also regenerate legs or pinchers lost while fighting or protecting themselves. (Hill, 2004; Shapiro, 2011; Texas Parks and Wildlife, 2009)

Communication and Perception

Callinectes sapidus is both colorful and highly visually responsive, yet almost all studies of their courtship have focused on chemical cues. In the underwater environment of C. sapidus, visual cues may function more rapidly and over a longer distance than chemical cues. Given that C. sapidus is aggressive and cannibalistic, visual cues may allow them to quickly evaluate potential mates from safer distances. The crabs will use color vision and color in mate choice with males having a preference for females with red claw dactyls. (Baldwin and Johnson, 2009)

Food Habits

Callinectes sapidus eats a large range of foods. Typically this species eats clams, oysters, and mussels as well as almost any vegetable or animal matter. This species will scavenge freshly dead animals but not long dead animals. The crabs will sometimes also eat young crabs. (Texas Parks and Wildlife, 2009)

  • Animal Foods
  • fish
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans
  • other marine invertebrates
  • Plant Foods
  • leaves

Predation

Callinectes sapidus is preyed on by the red drum, Atlantic croaker, herons, sea turtles and humans. They are also an important link in the food chain, being both predator and prey. They feed on fish, aquatic vegetation, mollusks, crustaceans, and annelids. (Steele, 1979; Texas Parks and Wildlife, 2009)

Ecosystem Roles

Parasites are very common on Callinectes sapidus. Barnacles, worms and leeches attach themselves to the outer shell; small animals called isopods live in the gills or on the abdomen; and small worms live in the muscles. Although C. sapidus is a host to many parasites, most of these do not affect the life of the crab. (Texas Parks and Wildlife, 2009)

Commensal/Parasitic Species
  • Barnacles
  • Leeches
  • Worms
  • Isopods

Economic Importance for Humans: Positive

The main positive economic importance of Callinectes sapidus for humans is for food. The blue crab is often eaten because the meat is tasty and can be prepared in a number of ways. Commercially, crabs are captured in traps that are rectangular, two feet wide, and are made of wire. The crabs are lured in by being baited with freshly dead fish. In some areas, crabs are also caught in trawls and by trotlines. Many people also crab since it is easy and inexpensive. Although there aren't any harvest limits, there is a 5-inch minimum body width as measured from spine to spine. (Texas Parks and Wildlife, 2009)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

There are no known adverse effects of Callinectes sapidus on humans.

Conservation Status

Callinectes sapidus is not listed by any conservation programs. (Hill, 2004; Texas Parks and Wildlife, 2009)

Contributors

samantha bodden (author), University of Wisconsin-Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Renee Mulcrone (editor), Special Projects.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

scavenger

an animal that mainly eats dead animals

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

Baldwin, J., S. Johnson. 2009. The importance of color in mate choice of the blue crab Callinectes sapidus. Journal of Experimental Biology, 212: 3762-3768. Accessed June 22, 2011 at http://www.ncbi.nlm.nih.gov/pubmed/19880739.

Hill, K. 2004. "Species name: Callinectes sapidus (blue crab)" (On-line). Smithsonian Marine Station at Fort Pierce. Accessed June 22, 2011 at http://www.sms.si.edu/irlspec/callin_sapidu.htm.

Jivoff, P., A. Hines. 2003. "Reproductive biology of blue crabs" (On-line). Smithsonian Environmental Research Center. Accessed June 22, 2011 at http://www.serc.si.edu/labs/fish_invert_ecology/bluecrab/reproduction.aspx.

Shapiro, L. 2011. "Callinectes sapidus M. J. Rathbun, 189" (On-line). EOL species rapid response. Accessed June 22, 2011 at http://eolspecies.lifedesks.org/pages/18927.

Steele, P. 1979. "A synopsis of the biology of the blue crab Callinectes sapidus Rathbun in Florida" (On-line pdf). Florida Fish and Wildlife Conservation Commission. Accessed June 22, 2011 at http://research.myfwc.com/engine/download_redirection_process.asp?file=79steele_1436.pdf&objid=20754&dltype=publication.

Texas Parks and Wildlife, 2009. "Blue crab (Callinectes sapidus)" (On-line). Texas Park and Wildlife. Accessed June 22, 2011 at http://www.tpwd.state.tx.us/huntwild/wild/species/bluecrab/.

Zinski, S. 2006. "Blue crab spawning" (On-line). Accessed June 22, 2011 at http://www.bluecrab.info/spawning.html.