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.
US Federal List: no special status
CITES: no special status
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.
Known Predators:
Anti-predator Adaptations: cryptic
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.
Range mass: 45 (high) g.
Range length: Carapace width 154 (high) mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes colored or patterned differently; male more colorful
There is currently little information available regarding the lifespan of speckled swimming crabs.
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.
Range depth: 0 to 68 m.
Habitat Regions: temperate ; tropical ; saltwater or marine
Aquatic Biomes: benthic ; coastal
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.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
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.
Animal Foods: reptiles; fish; carrion ; mollusks; aquatic or marine worms; aquatic crustaceans; other marine invertebrates
Plant Foods: algae
Other Foods: detritus
Primary Diet: carnivore (Scavenger ); detritivore
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.
Ecosystem Impact: biodegradation
Commensal/Parasitic Species:
Speckled swimming crabs are commercially gathered in Brazil as food and are considered to have an excellent flavor.
Positive Impacts: food
There are no known adverse effects of speckled swimming crabs on humans.
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.
Development - Life Cycle: metamorphosis ; indeterminate growth
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.
Communication Channels: visual ; tactile ; acoustic ; chemical
Other Communication Modes: pheromones
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
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.
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.
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.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
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.
Parental Investment: female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female)
Arenaeus cribrarius, the speckled swimming crab, is a species of swimming crab in the family Portunidae.[2][3][4]
The crabs can be found from Massachusetts, U.S. to areas in Argentina.[5] They are common in shallow water on sand in ocean beaches, but can be found in depths up to two hundred feet (61 m) deep.[6] They are typically found in temperate or tropical waters between eleven and twenty-nine degrees Celsius with a salinity between twenty-eight and thirty-five PSU.[7] Arenaeus cribrarius often bury themselves entirely in sand, but leave a gap for water to pass to their gills.[6] The crabs maintain the gap by clearing the sand with their claws and hairs around their mouth area.[6] Arenaeus cribrarius is a nocturnal and solitary organism, which only interacts with other crabs of its species when it wants to breed.[7]
The Speckled swimming crab eats primarily detritus, but have also been recorded eating fish, mollusks, and other crustaceans.[7] They ambush prey that go near their buried bodies.[7] Speckled swimming crabs have been recorded capturing sea turtle hatchlings.[7] Sea turtles are the primary predator to Arenaeus cribrarius.[7] The crabs use their coloration and spines to ward off such predators.[7]
They share a very similar overall shape with the Atlantic Blue Crab.[6] The carapace of a Speckled swimming crab is light brown, light maroon, or olive with many white or tan irregular round spots.[6] The males tend to be more colorful.[6] The carapace can reach lengths between 4.5 and 6 inches wide (~120-150mm).[6] Each side of the carapace consists of nine lateral teeth with the last extending outward.[6] Between the eye sockets there are six partially fused frontal teeth.[6]
Arenaeus cribrarius has ten legs since it is a part of the order decapoda.[6] The first four pairs of legs have yellow tips and are used for walking.[6] These are referred to as broad pereopods.[6] They fifth pair of pereopods are used for swimming.[6] They are a wide flattened paddle shape.[6] Overall, Arenaeus cribrarius can weigh as much as forty-five grams (1.6 ounces).[6]
When the Arenaeus cribrarius reaches sexual maturity around five to seven years of age they begin to mate.[6] Arenaeus cribrarius breed year-round and are polygynandrous.[8] The male crab, who is between molts, will select a premolt female who is expressing courtship behavior.[9] The crabs communicate with one another through chemical, visual, and acoustic cues.[8] The male then carries the female for thirty days in a precopulatory position under his body until the female molts.[7][9] When the female's shell is still soft the male will invert her to position themselves with their abdomens in contact together.[7] The male then transfers his spermatophores to her gonopores.[7] Once mating has occurred, the eggs will spawn around fifty-seven days later and will have an fecundity between 135,000 and 680,000.[9] Nauplia will hatch from the Speckled swimming crab eggs around eighteen days and will grow into the first stage of crab thirteen days later.[9] The average age for a Speckled swimming crab is two years.[9]
In some parts of the world Arenaeus cribrarius is important in fisheries, particularly along the Brazilian coast.[9] The crab is harvested for its meat and residual proteins are used to produce fertilizers and feed for livestock.[9] Along with the consumption of meat, the Speckled swimming crab is harvested for its byproducts.[9] Chitin can be extracted from the crab and used in products like adhesives, cosmetics, photographic emulsions, and anticoagulants.
Arenaeus cribrarius, the speckled swimming crab, is a species of swimming crab in the family Portunidae.
