These crabs communicate using touch, chemical signals, and visual cues. Antennae are used by larvae as tactile receptors. Adults have fine spine-like projections near the tip of each leg, which are used for chemoreception (pheromones) as well as sensing vibration and other tactile input. This species has compound eyes and use their acute vision to find prey.
Communication Channels: visual ; tactile ; chemical
Other Communication Modes: pheromones
Perception Channels: visual ; tactile ; vibrations ; chemical
This species has not been evaluated by IUCN and is not currently considered endangered or threatened.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Females carry their eggs under their bodies until they hatch, when they help to release larvae from eggs by using their chelae to disturb their egg mass and wave their bodies in shallow water. After hatching, larvae swim out to deeper waters where they consume phytoplankton and undergo a series of quick molts. More body segments are added after each molt, and two appendages, used for swimming, are added to each new segment. Eventually (an exact number of molts is not known) larvae undergo metamorphosis, becoming juveniles. Juveniles are similar in appearance to adults but are smaller and darker, usually dark green or black with dark red limbs. Juveniles make their way back to rocky shorelines, where they feed as adults and continue to grow by molting, achieving greater size and brighter coloration with each molt. After this puberty molt, the chelae of males grow quickly and females' abdomens become larger in preparation to hold eggs. Adults grow throughout their lives, with longer periods of time between each molt as they age. This species can regenerate lost limbs.
Development - Life Cycle: metamorphosis ; indeterminate growth
If bothered, these crabs may give a painful pinch or squirt water on their antagonizers. Other than these very minor, avoidable problems, this species presents no adverse effects to humans.
Negative Impacts: injures humans
Red rock crabs are used, alive or dead, as bait for shoreline fishing. They also help maintain clean shorelines, which is particularly important in areas that rely on tourism. They are sometimes available in the pet trade.
Positive Impacts: pet trade ; ecotourism
Red rock crabs feed on dead animals and algae, cleaning up beaches and rocks along coastlines. They help control some bird populations by eating their eggs. They also provide a source of food for many animals that live along coastlines.
These crabs have been known to pick ticks from marine iguanas, suggesting a mutually beneficial relationship between these species.
Red rock crabs are hosts to a number of parasites, including isopods.
Ecosystem Impact: biodegradation
Mutualist Species:
Commensal/Parasitic Species:
Red rock crabs feed on sponges, mollusks, crustaceans, fishes, carrion (mainly seals and birds), young sea turtles, bird eggs and droppings, algae, and bat guano. As larvae, they feed on phytoplankton. Most food is obtained by scavenging along rocks and the shoreline. Live fish may be caught in shallow waters with their claws and mollusks, such as clams, may be found during low tides. These crabs are known to feed on ticks that they remove from live marine iguanas. They have been known to resort to cannibalism when populations densities are high or food is scarce. Red rock crabs use their claws to scrape food off rocks or capture live animals as well as to move the food into their mouths, and can break open tough material like mollusk and crab shells or corals that may wash ashore.
Animal Foods: birds; reptiles; fish; eggs; carrion ; terrestrial non-insect arthropods; mollusks; aquatic crustaceans; other marine invertebrates
Plant Foods: algae; phytoplankton
Other Foods: detritus ; dung
Primary Diet: carnivore (Eats terrestrial vertebrates, Piscivore , Eats eggs, Eats non-insect arthropods, Molluscivore , Eats other marine invertebrates, Scavenger ); herbivore (Algivore); omnivore ; planktivore ; detritivore ; coprophage
Red rock crabs can be found along coasts of subtropical and tropical North America, South America, and the islands occuring within this range in both the Pacific and Atlantic Oceans. They are most commonly found in coastal areas of Baja, California, from Mexico to Peru, Ecuador, the Caribbean, Brazil, Florida, and the Galapagos Islands.
Biogeographic Regions: nearctic (Native ); neotropical (Native ); oceanic islands (Native ); atlantic ocean (Native ); pacific ocean (Native )
Adult red rock crabs live along rocky shorelines, usually at or above the spray line in tropical and subtropical North America, South America, and islands occuring around this latitude in both the Pacific and Atlantic oceans. When it comes time for eggs, carried by females, to hatch, females go to a calm shallow area so larvae can drop straight into the water. Red rock crab larvae are free swimming in shallow waters just off-shore. After they metamorphose, juveniles makes their way back to rocks on the shore, their primary habitat.
Range elevation: 0 to 5 m.
Average elevation: 1 m.
Habitat Regions: tropical ; terrestrial ; saltwater or marine
Aquatic Biomes: coastal
Other Habitat Features: intertidal or littoral
Red rock crabs are known to live for up to 10 years in captivity. Average lifespan in the wild is unknown and limited mainly by predation.
Range lifespan
Status: captivity: 10 (high) years.
Typical lifespan
Status: captivity: 5 to 10 years.
Average lifespan
Status: captivity: 7 years.
Red rock crabs are vividly multi-colored. Adults are typically bright yellow and red with black stripes around the edges of their carapaces and black or green dots near their eyes. Leg joints are often black or a dark green color, each leg ending with a bright orange or yellow tip, and claws are typically bright red. Their underbellies are usually pale white. These crabs are typically darker in color as young adults, growing brighter with age. Carapaces range in size from 5-8 cm in width. They have four large segmented walking legs with spine-like projections near the tip of each leg, and two arms with pinchers. They have two eyes on short stalks at the fronts of their bodies. Males tend to be slightly smaller than females, and their right claws are slightly larger than their left claws.
Larvae (zoea) are about 0.5 mm long and have smooth bodies with long spines and a slender, curved abdomen ending in a forked telson. Their abdomens have five somites, eight legs, two arms with minimal claws and sessile eyes. They have four antennae on their heads.
Range length: 5 to 8 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: female larger; sexes shaped differently
These crabs have many predators including a variety of birds, octopuses, eels, fishes, and cats. They try to avoid predation by moving quickly and hiding in rock crevices during daytime hours. When cornered, they will shoot a stream of water to scare a predator away, pinch with their claws, or drop a leg in order to escape. They rely on their thick carapaces for defense.
Known Predators:
During courtship, males will battle for females by first facing each other then side stepping right and left in tandem while touching claws. If neither crab retreats, one crab will lunge at the other and try to grab his rival's claws and break them off; if this occurs, the retreating crab is chased away by the victor, who now has access to a nearby female. This male deposits his sperm into the spermathecae of athe female; the release of sperm is aided by secretions from gonopod tegumental glands, which lubricate the narrow ejaculatory canal and thin out the ejaculate. After receiving sperm, females release their fertilized eggs, storing remaining sperm in their spermathecae. Eggs remain suspended on a female's belly for protection until hatching. Females will only mate again when all stored sperm has been used, which is dependent on how many eggs are produced at a time. While females will only mate with one male at a time, males and females may have multiple partners over a breeding season.
Mating System: polygynandrous (promiscuous)
Breeding occurs year round, particularly in more tropical ranges, but egg hatching seems to coincide with full moons. Males mate often but must wait 10-20 days to regenerate sperm. Females mate less often than males, only when stored sperm has been depleted; depletion time depends on how many eggs are produced, anywhere from 20-100 per clutch, which is dependent on resource abundance and female size. Females molt shortly following hatching a clutch of eggs and will lay eggs again soon after, typically every 24 days. Females carry eggs on their underbellies. Eggs may take up to three weeks to hatch, at which time embryos are aided in hatching by females. Exact age at sexual maturity is unknown, although a puberty molt has been noted at a carapace length of 51.4 mm for males and 33.8 mm for females. After mating, males and females return to their solitary lifestyles.
Breeding interval: Sally Lightfoot crabs may breed multiple times throughout the year.
Breeding season: Breeding season for this species is year-round.
Range number of offspring: 20 to 100.
Average gestation period: 3 weeks.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous ; sperm-storing ; delayed fertilization
Male red rock crabs exhibit no parental involvement following fertilization. Females carry fertilized eggs underneath their bodies to protect them from predators and keep them out of direct sunlight. Ocean spray and water from females' bodies keep her eggs moist. When it is time for eggs to hatch, females aid this process by rubbing them between their bodies and a rough surface, over shallow water. Larvae drop into the water and are completely independent.
Parental Investment: female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female)
