Grapsus grapsus

Sally Lightfoot crab

Features
By Nick Miller

Geographic Range

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.

Habitat

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.

Physical Description

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.

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently

Development

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.

Reproduction

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.

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.

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

Lifespan/Longevity

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.

Behavior

The larvae of this species are free swimming; it is unknown whether they stay in groups and what their strategies may be for protection from predation. Juveniles typically live in groups, while adult crabs live solitary lives, only coming together around food sources or for mating; there is no notable interaction between individuals otherwise, even when they encounter each other. These crabs are typically most active during morning and afternoon, when they search rocks in coastal zones for food or mates. This timing reduces exposure to predators and prevents dessication during times of high heat. They move very quickly and with great agility, and can cling tightly to rocks when hit by surf while feeding. When not out searching for food and mates, red rock crabs spend their time in the cracks of rocks or other shaded, small areas into which they can deeply wedge themselves for protection from predators. If this fails to protect them, they may spit a stream of water at a predator, use their claws for protection, or even shed a leg, which can be grown back.

Home Range

Individuals do not have selected territories, tending to wander about rocky shorelines looking for food and mates before returning to nonspecific rock outcroppings.

Communication and Perception

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.

Food Habits

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

Predation

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.

Ecosystem Roles

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.

Mutualist Species
Commensal/Parasitic Species

Economic Importance for Humans: Positive

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.

Economic Importance for Humans: Negative

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

Conservation Status

This species has not been evaluated by IUCN and is not currently considered endangered or threatened.

Encyclopedia of Life

Contributors

Nick Miller (author), University of Michigan-Ann Arbor, Jeremy Wright (editor), University of Michigan-Ann Arbor.

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

native range

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

Neotropical

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

World Map

native range

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

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

native range

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

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

native range

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

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

native range

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

tropical

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

terrestrial

Living on the ground.

saltwater or marine

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

coastal

the nearshore aquatic habitats near a coast, or shoreline.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

ectothermic

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

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.

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.

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.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

iteroparous

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).

year-round breeding

breeding takes place throughout the year

sexual

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

fertilization

union of egg and spermatozoan

internal fertilization

fertilization takes place within the female's body

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

female parental care

parental care is carried out by females

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

active at dawn and dusk

motile

having the capacity to move from one place to another.

solitary

lives alone

visual

uses sight to communicate

tactile

uses touch to communicate

chemical

uses smells or other chemicals to communicate

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

visual

uses sight to communicate

tactile

uses touch to communicate

vibrations

movements of a hard surface that are produced by animals as signals to others

chemical

uses smells or other chemicals to communicate

carrion

flesh of dead animals.

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

biodegradation

helps break down and decompose dead plants and/or animals

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

carnivore

an animal that mainly eats meat

piscivore

an animal that mainly eats fish

molluscivore

eats mollusks, members of Phylum Mollusca

scavenger

an animal that mainly eats dead animals

herbivore

An animal that eats mainly plants or parts of plants.

omnivore

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

planktivore

an animal that mainly eats plankton

detritivore

an animal that mainly eats decomposed plants and/or animals

coprophage

an animal that mainly eats the dung of other animals

References

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Hartnoll, R. 2009. Sexual Maturity and Reproductive Strategy of the Rock Crab Grapsus Adscensionis (Osbeck, 1765) (Brachyura, Grapsidae) on Ascension Island. Crustaceana , 82/3: 275-291. Accessed February 07, 2013 at http://booksandjournals.brillonline.com/content/10.1163/156854009x409090 .

IUCN, 2012. "The IUCN Red List of Threatened Species" (On-line). Accessed February 07, 2013 at http://www.iucnredlist.org/search .

Koneeny, M. 1987. Food Habits and Energetics of feral House Cats in the Galapagos Islands. Oikos , 50: 24-32.

Markham, J. 2002. A New Species of Leidya Cornalia and Panceri, 1861, and the First Record of the Genus Lobocepon Nobili, 1905, Both From the Estern Pacific Ocean, With a Review of the Parasites of Grapsid Crabs Woldwide (Isopoda, Bopyridae, Ioninae). Pp. 330 in Modern Approaches to the Study of Crustacea . New York: Kluwer Academic/Plenum Publishers. Accessed February 07, 2013 at http://books.google.com/books?id=H_u6HHgd2bMC&pg=PA330&lpg=PA330&dq=parasite+grapsus+grapsus&source=bl&ots=G0h5Lsq1uj&sig=W6cqzcNLzO7FIL5u1H0fCLWIy1M&hl=en&sa=X&ei=l_QTUYjkA6qB0QH95oHIBA&ved=0CBgQ6AEwAA#v=onepage&q&f=false .

Mejia, M. 1995. "Decapoda Images" (On-line image). Tree of Life web project. Accessed January 29, 2012 at tolweb.org/images/Decapoda/6308 .

Raymond, B., A. Fenner. 1990. Decapod and Stomatopod Crustacea from Ascension Island, South Atlantic Ocean. Smithsonian Contributions to Zoology , 503: 503.

Sazima, I., L. Bastos de Almeida. 2009. The bird kraken: octopus preys on a sea bird at an oceanic island in the tropical West Atlantic. Marine Biodiversity Records , 1: 47.

Snow, J. 1998. "Sally Lightfoot Crab, Abuete Negro, (Grapsus grapsus)" (On-line). mexfish.com. Accessed January 29, 2012 at http://www.mexfish.com/fish/salltft/salltft.htm .

Vaske, T., C. Vooren, R. Lessa. 2003. Feeding strategy of yellowfin tuna ( Thunnus albacares ), and wahoo ( Acanthocybium solandri ) in the Saint Peter and Saint Paul Archipelago, Brazil. B. Inst. Pesca, São Paulo , 1: 173-181.

Warner, G. 1977. The Biology of Crabs . London: Elek Science.

Weisz, N. 2012. "Grapsus grapsus — Overview Sally Lightfoot crab" (On-line). Accessed January 29, 2012 at http://eol.org/pages/1021865/overview .

1978. Sally Lightfoot. Sea Frontiers , 24/2: 2-7.

To cite this page: Miller, N. 2013. "Grapsus grapsus" (On-line), Animal Diversity Web. Accessed {%B %d, %Y} at https://animaldiversity.org/accounts/Grapsus_grapsus/

Last updated: 2013-45-13 / Generated: 2025-10-03 01:10

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