Arenaeus cribrariusspeckled swimming crab

Geographic Range

Speckled swimming crabs, Arenaeus cribrarius, are found on the Atlantic coast of North, Central and South America, ranging from the state of Massachusetts in the United States to Uruguay. (Tavares, 2009)


Speckled swimming crabs live along sandy beaches in shallow to deep water up to 68 m in depth. They have been found in waters 11 to 28.6 °C in temperature and 27.5 to 35 PSU in salinity. When on land, they prefer the foreshore area of beaches in fine mixed sands with low organic matter. (Edlin Guerra-Castro and Carmona-Suárez, 2007; Tavares, 2009)

  • Range depth
    0 to 68 m
    0.00 to 223.10 ft

Physical Description

The carapace of speckled swimming crabs is twice as wide as it is long and can be as wide as 154 mm. The carapace ranges in color from light reddish brown to olive brown and is covered with many small, rounded white spots. The chelipeds (claws) are short and narrow. They have 4 pairs of short, broad pereopods (walking legs) with yellow tips. The fifth pair of pereopods is flattened and paddle-shaped. The perepods and the lower surface of the carapace are densely covered with hair. Speckled swimming crabs can weigh as much as 45 g. (Tavares, 2009)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • male more colorful
  • Range mass
    45 (high) g
    1.59 (high) oz
  • Range length
    Carapace width 154 (high) mm


Speckled swimming crabs have 4 main stages of life; they begin as planktonic zoea, become megalops, benthic juveniles, and finally adults. Speckled swimming crabs pass through 8 stages as zoea, each lasting 4 to 6 days. After each stage, they molt and develop into the next stage of zoea. The body of zoea primarily consists of the head. They have a single dorsal spine in the middle of the head and a long rostrum extending downward beneath the eyes. Zoea also have a long abdomen. Megalops resemble a tiny lobster. During this stage, the head slightly elongates, the dorsal spine, located posterior to the head, shortens, they eyes become stalked, and small chelipeds develop. The abdomen remains long and has now developed prominent peropods. After 13 days, megalops metamorphose into a juvenile crab, with a prominent carapace with two lateral spines projecting from the outer edges. Juveniles have larger chelipeds and a flattened pair of 5th peropods. If juveniles successfully survive, they eventually become adult crabs. (Stuck and Truesdale, 1988)


Between molting periods, male speckled swimming crabs express a courtship display to attract premolted females. The display intensifies when a potential mate is visually recognized. After a female is chosen, the male grasps the female with his chelipeds and holds her under himself for 25 to 35 days until the female molts. Soon after the female molts, when her shell is still soft, the male inverts her so they are positioned abdomen to abdomen. He penetrates her with specially-modified pleopods, transferring spermatophore packages into her gonopores. After copulation, he continues to carry her for 24 to 36 days until her shell has hardened completely. Speckled swimming crabs are polygynandrous, meaning males and females have multiple mates. (Pinheiro and Fransozo, 1999)

Speckled swimming crabs breed year-round, although breeding is more common in the summer and winter, when water temperature oscillations are reduced. Females can produce between 135,000 and 682,000 eggs. Like other members of the family Portunidae, speckled swimming crabs communicate during the reproductive period, which can occur through visual, acoustic, chemical and tactile cues. Speckled swimming crabs reach sexual maturity when their carapace is between 60 and 64 mm in width, which generally occurs around 60 to 80 days of age. (Pinheiro and Franosozo, 1998; Pinheiro and Fransozo, 1999; Pinheiro and Fransozo, 2002; Pinheiro and Terceiro, 2000)

  • Breeding season
    Speckled swimming crabs breed year-round, but breeding is more common in summer and winter.
  • Range number of offspring
    135,000 to 682,000
  • Range age at sexual or reproductive maturity (female)
    60 to 80 days
  • Range age at sexual or reproductive maturity (male)
    60 to 80 days

After copulation, female speckled swimming crabs extrude fertilized eggs and carry the egg mass beneath her abdomen with specially-modified pleopods. Females protect their egg mass and fan it with their pleopods to oxygenate the developing eggs and keep them clean. After larvae hatch and are released into the water column, there is no further parental care. (Pinheiro and Fransozo, 1999)


There is currently little information available regarding the lifespan of speckled swimming crabs.


Speckled swimming crabs are nocturnal and solitary, coming together with other members of their species only to breed. When threatened, they automatically assume a defensive position with their chelipeds raised up in the air. Speckled swimming crabs migrate between shallower and deeper waters as they forage and evade predators. (Edlin Guerra-Castro and Carmona-Suárez, 2007; Frick, 2003)

  • Range territory size
    16,625 (high) m^2

Home Range

Speckled swimming crabs in Ensenada de La Vela in the Venezuelan Caribbean have a home range of 16,625 sq m. (Edlin Guerra-Castro and Carmona-Suárez, 2007)

Communication and Perception

As with other crustaceans, speckled swimming crabs communicate through visual, acoustic, chemical and tactile cues. The associated senses are also used in perceiving the environment. (Pinheiro and Fransozo, 1999)

Food Habits

Speckled swimming crabs primarily eat detritus from the ocean floor. They also eat crustaceans, fish, and molluscs. Like most crabs, speckled swimming crabs are opportunistic scavengers, and they have even been recorded chasing down, capturing, and preying on hatchling loggerhead sea turtles. Speckled swimming crabs bury themselves near the breaker zone and ambush prey that crawl or swim near them, seizing the prey with their chelipeds. Crabs then rebury themselves, which may help to subdue captured prey. (Carmona-Suárez and Conde, 2005; Frick, 2003)

  • Animal Foods
  • reptiles
  • fish
  • carrion
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans
  • other marine invertebrates
  • Plant Foods
  • algae


The only known predators of speckled swimming crabs other than humans are two species of sea turtles: loggerhead sea turtles and Kemp's Ridley sea turtles. The camouflaged pattern on their carapace helps to conceal speckled swimming crabs in the sand from predators. Also useful against predators are two strong, sharp, slightly upcurved spines on the side of the body. Additionally, the front edge of their carapace is serrated. Speckled swimming crabs are least vulnerable to predation when fully grown, when their spines and camoflouging pattern are fully developed. (Frick, 2003; Tavares, 2009)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

As a scavenger, speckled swimming crabs recycle nutrients bound within dead organisms back into the food web. As a mesopredator, they help maintain invertebrate biodiversity within their community. They also serves as prey for larger predators through all of their developmental stages. Speckled swimming crabs also act as host to parasitic barnacles, including Chelonibia patula, Octolasmis lowei, Octolasmis mulleri, as well as a nemertean worm Carcinonemertes carcinophila imminuta. (Mantelatto, et al., 2003)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Speckled swimming crabs are commercially gathered in Brazil as food and are considered to have an excellent flavor. (Carmona-Suárez and Conde, 2002)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

There are no known adverse effects of speckled swimming crabs on humans.

Conservation Status

Speckled swimming crabs have not been evaluated by the IUCN or the US Fish and Wildlife Service. They are, however, commercially gathered in Brazil which likely influences population sizes. (Carmona-Suárez and Conde, 2002)


Abel Sandoval (author), San Diego Mesa College, Thomas Wroblewski (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Gail McCormick (editor), Animal Diversity Web Staff.




World Map



World Map


uses sound to communicate



bilateral symmetry



helps break down and decompose dead plants and/or animals


an animal that mainly eats meat


flesh of dead animals.


uses smells or other chemicals to communicate


the nearshore aquatic habitats near a coast, or shoreline.




an animal that mainly eats decomposed plants and/or animals





female parental care

parental care is carried out by females


union of egg and spermatozoan







indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

internal fertilization

fertilization takes place within the female's body






having the capacity to move from one place to another.


specialized for swimming

native range



active during the night







saltwater or marine



an animal that mainly eats dead animals

seasonal breeding

breeding is confined to a particular season


remains in the same area




lives alone


uses touch to communicate








uses sight to communicate

year-round breeding

breeding takes place throughout the year


Carmona-Suárez, C., J. Conde. 2005. The natural diet of Arenaeus cribrarius (Decapoda, Brachyura, Portunidae) on two arid beaches in western Venezuela. Crustaceana, 78(5): 525-541.

Carmona-Suárez, C., J. Conde. 2002. Local distribution and abundance of swimming crabs (Callinectes spp. and Arenaeus cribrarius) on a tropical arid beach. Fish Bull, 100(1): 11-25. Accessed March 07, 2010 at

Edlin Guerra-Castro, C., J. Carmona-Suárez. 2007. Activity patterns and zonation of the swimming crabs Arenaeus cribrarius and Callinectes ornatus. Journal of Crustacean Biology, 27(1): 49-58.

Frick, M. 2003. "The Surf Crab (Arenaeus cribrarius): A Predator and Prey Item of Sea Turtles" (On-line). Accessed March 07, 2010 at

Mantelatto, F., J. O'Brian, R. Biagi. 2003. Parasites and Symbionts of Crabs from Ubatuba Bay, São Paulo State, Brazil. Comparative Parasitology, 70(2): 211-214.

Pinheiro, M., A. Franosozo. 1998. Sexual maturity of the speckled swimming crab Arenaeus cribrarius (Lamarck, 1818) (Decapoda, Brachyura, Portunidae), in the Ubatuba littoral, Sao Paulo State, Brazil. Crustaceana, 71(4): 434-452.

Pinheiro, M., A. Fransozo. 2002. Reproduction of the speckled swimming crab Arenaeus cribrarius (Brachyura: Portunidae) on the Brazilian coast near 23º 30' S. Journal of Crustacean Biology, 22(2): 416-428.

Pinheiro, M., O. Terceiro. 2000. Fecundity and reproductive output of the speckled swimming crab Arenaeus cribrarius (Lamarck, 1818) (Brachyura, Portunidae). Crustaceana, 73(9): 1121-1137.

Pinheiro, M., A. Fransozo. 1999. Reproductive behavior of the swimming crab Arenaeus cribrarius (Lamarck, 1818) (Crustacea, Brachyura, Portunidae) in Captivity. Bulletin of Marine Science, 64(2): 243-253.

Stuck, K., F. Truesdale. 1988. Larval development of the speckled swimming crab, Arenaeus cribrarius (Decapoda: Brachyura: Portunidae) Reared in the Laboratory. Bulletin of Marine Science, 42(1): 101-132.

Tavares, M. 2009. "True Crabs" (On-line). Accessed March 07, 2010 at