''Grapsus grapsus'' is one of the most common

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

s along the western coast of the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...

. It is known as the red rock crab, or, along with crabs such as ''

Percnon gibbesi ''Percnon gibbesi'' is a species of crab. It is one of at least two species commonly called "Sally Lightfoot" (the other being the semi-terrestrial ''Grapsus grapsus'' from the Pacific coast of the Americas), and is also referred to as the ''nim ...

'', as the Sally Lightfoot crab.

Distribution

''Grapsus grapsus'' is found along the Pacific coast of

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

, and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

(as far south as northern

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

), and on nearby islands, including the

Galápagos Islands The Galápagos Islands (Spanish: , , ) are an archipelago of volcanic islands. They are distributed on each side of the equator in the Pacific Ocean, surrounding the centre of the Western Hemisphere, and are part of the Republic of Ecuador ...

. It is also found along the Atlantic coast of South America, but is replaced in the eastern Atlantic Ocean ( Ascension Island and

West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Maurit ...

) by its congener ''

Grapsus adscensionis ''Grapsus adscensionis'' is a species of crab found in the eastern Atlantic Ocean. Distribution ''Grapsus adscensionis'' is found in parts of the Atlantic coast of Africa and in several groups of Atlantic islands such as Macaronesia, Saint Hele ...

''.

Description

''Grapsus grapsus'' is a typically shaped crab, with five pairs of legs, the front two bearing small, blocky, symmetrical

chelae A chela ()also called a claw, nipper, or pinceris a pincer (biology), pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are ...

(claws). The other legs are broad and flat, with only the tips touching the substrate. The crab's round, flat

carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...

is slightly longer than . Young ''G. grapsus'' are black or dark brown in colour and are camouflaged well on the black

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

coasts of volcanic islands. Adults are quite variable in colour; some are muted brownish-red, some mottled or spotted brown, pink, or yellow.

Taxonomy

''Grapsus grapsus'' was first described by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

in the 1758 10th edition of ''

Systema Naturae ' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomen ...

'' as "''Cancer grapsus''". The species ''Grapsus grapsus'' and '' G. adscensionis'' were not separated until 1990. The latter is found in the eastern

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

, while the former is not. While the validity of the separation into two species has been questioned, there are constant morphological differences in the colouration of the pereiopods and the form of the first zoea larva, and no evidence for any genetic connection between the two populations, and they are generally treated as separate species.

Ecology and behavior

This crab lives among the rocks at the often turbulent, windy shore, just above the limit of the sea spray. It feeds on

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...

e primarily, sometimes sampling other plant matter and dead animals. It is an agile crab, capable of leaping, and consequently hard to catch. Not considered very edible by humans, it is used as bait by fishermen. It is preyed upon by the chain moray eel, '' Echidna catenata,'' as well as by octopuses. ''G. grapsus'' has been observed in an apparent

cleaning symbiosis Cleaning symbiosis is a mutually beneficial association between individuals of two species, where one (the cleaner) removes and eats parasites and other materials from the surface of the other (the client). Cleaning symbiosis is well-known amon ...

taking

tick Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...

s from

marine iguana The marine iguana (''Amblyrhynchus cristatus''), also known as the sea iguana, saltwater iguana, or Galápagos marine iguana, is a species of iguana found only on the Galápagos Islands (Ecuador). Unique among modern lizards, it is a marine repti ...

s on the Galápagos Islands. ''Grapsus grapsus'' was collected by

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...

during his voyages on HMS ''Beagle'', and also by the first comprehensive study of the fauna of the Gulf of California, carried out by

Ed Ricketts Edward Flanders Robb Ricketts (May 14, 1897 – May 11, 1948) was an American marine biologist, ecologist, and philosopher. He is best known for ''Between Pacific Tides'' (1939), a pioneering study of intertidal ecology. He is also known as a men ...

, together with

John Steinbeck John Ernst Steinbeck Jr. (; February 27, 1902 – December 20, 1968) was an American writer and the 1962 Nobel Prize in Literature winner "for his realistic and imaginative writings, combining as they do sympathetic humor and keen social ...

and others. Steinbeck records:

These little crabs, with brilliant
cloisonné Cloisonné () is an ancient technique for decorating metalwork objects with colored material held in place or separated by metal strips or wire, normally of gold. In recent centuries, vitreous enamel has been used, but inlays of cut gemstones, ...
carapaces, walk on their tiptoes, They have remarkable eyes and an extremely fast reaction time. In spite of the fact that they swarm on the rocks at the Cape an Lucas and to a less degree inside the Gulf f California they are exceedingly hard to catch. They seem to be able to run in any of four directions; but more than this, perhaps because of their rapid reaction time, they appear to read the mind of their hunter.

Gallery

Zayapa (Grapsus grapsus), Las Bachas, isla Baltra, islas Galápagos, Ecuador, 2015-07-23, DD 30.JPG, Baltra, Galapagos Islands Zayapa (Grapsus grapsus), Las Bachas, isla Santa Cruz, islas Galápagos, Ecuador, 2015-07-23, DD 25.jpg, Baltra, Galapagos Islands. Zayapa (Grapsus grapsus), Cerro Brujo, isla de San Cristóbal, islas Galápagos, Ecuador, 2015-07-24, DD 152.JPG, Juvenile in San Cristobal, Galápagos. Zayapa (Grapsus grapsus), Cerro Brujo, isla de San Cristóbal, islas Galápagos, Ecuador, 2015-07-24, DD 151.JPG, Adult in San Cristobal, Galápagos. Zayapa (Grapsus grapsus), Punta Pitt, isla de San Cristóbal, islas Galápagos, Ecuador, 2015-07-24, DD 84.JPG, Adult in Punta Pitt (San Cristobal), Galápagos. Zayapa (Grapsus grapsus), Punta Pitt, isla de San Cristóbal, islas Galápagos, Ecuador, 2015-07-24, DD 79.JPG, Group in San Cristobal, Galápagos. Zayapa (Grapsus grapsus), Las Bachas, isla Santa Cruz, islas Galápagos, Ecuador, 2015-07-23, DD 21.jpg, Adult in Baltra, Galápagos. Zayapa (Grapsus grapsus), Punta Pitt, isla de San Cristóbal, islas Galápagos, Ecuador, 2015-07-24, DD 83.JPG, View of the lower part Galápagos Sally Lightfoot crab (Grapsus grapsus).jpg, Adult from the front

References

External links

* * {{Taxonbar, from=Q181075 Grapsidae Crustaceans of the eastern Pacific Ocean Crustaceans described in 1758 Taxa named by Carl Linnaeus Marine fauna of the Gulf of California Western Central American coastal fauna Galápagos Islands coastal fauna Western South American coastal fauna