Speckled swimming crabs, (Tavares, 2009), are found on the Atlantic coast of North, Central and South America, ranging from the state of Massachusetts in the United States to Uruguay.
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
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)
- Mating System
- polygynandrous (promiscuous)
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)
- Key Reproductive Features
- seasonal breeding
- year-round breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- 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)
- Parental Investment
- female parental care
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
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)
- Other Communication Modes
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
- aquatic or marine worms
- aquatic crustaceans
- other marine invertebrates
- Plant Foods
- Other Foods
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
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)
- Ecosystem Impact
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
Economic Importance for Humans: Negative
There are no known adverse effects of speckled swimming crabs on humans.
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.
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.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
- 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.
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.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
an animal that mainly eats decomposed plants and/or animals
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- female parental care
parental care is carried out by females
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
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.
- indeterminate growth
Animals with indeterminate growth continue to grow throughout their lives.
- internal fertilization
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
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.
having the capacity to move from one place to another.
specialized for swimming
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
chemicals released into air or water that are detected by and responded to by other animals of the same species
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- saltwater or marine
mainly lives in oceans, seas, or other bodies of salt water.
an animal that mainly eats dead animals
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
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).
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
movements of a hard surface that are produced by animals as signals to others
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 http://fishbull.noaa.gov/1001/car.pdf.
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 http://www.seaturtle.org/mtn/archives/mtn99/mtn99p16.shtml.
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 ftp://ftp.fao.org/docrep/fao/009/y4160e/y4160e23.pdf.