The Atlantic ghost crab, ''Ocypode quadrata'', is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

ghost crab Ghost crabs are semiterrestrial crabs of the subfamily Ocypodinae. They are common shore crabs in tropical and subtropical regions throughout the world, inhabiting deep burrows in the intertidal zone. They are generalist scavengers and predator ...

. It is a common species along the

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

coast of the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, where it is the only species of ghost crab; its range of distribution extends from its northernmost reach on beaches in

Westport, Massachusetts Westport (Massachusett language, Massachusett: ) is a New England town, town in Bristol County, Massachusetts, Bristol County, Massachusetts, United States. The population was 16,339 at the 2020 census. The village of North Westport, Massachusett ...

, south along the coasts of the tropical Western Atlantic Ocean to the beach of Barra do Chui, in

Rio Grande do Sul Rio Grande do Sul (, ; ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative units of Brazil#List, fifth-most populous state and the List of Brazilian s ...

in southern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Description

Adults are grayish or the color of

straw Straw is an agricultural byproduct consisting of the dry wikt:stalk, stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the crop yield, yield by weight of cereal crops such as barley, oats, rice, ry ...

, and around wide at maturity. They must return to water periodically to moisten their

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

s, and when

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e must be released into the sea, but are otherwise

terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...

. Their stalked

compound eye A compound eye is a Eye, visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidium, ommatidia, which are tiny independent photoreception units that consist of a cornea, lens (anatomy), lens, and p ...

s can swivel to give them 360° vision. Young crabs are cryptically colored to blend in with their sandy habitats.

Distribution

Atlantic ghost crabs are found from Santa Catarina north to Massachusetts, USA. They have been recorded in

Block Island Block Island is an island of the Outer Lands coastal archipelago in New England, located approximately south of mainland Rhode Island and east of Long Island's Montauk Point. The island is coterminous with the town of New Shoreham, Rhode Isl ...

Rhode Island Rhode Island ( ) is a state in the New England region of the Northeastern United States. It borders Connecticut to its west; Massachusetts to its north and east; and the Atlantic Ocean to its south via Rhode Island Sound and Block Is ...

Nantucket Nantucket () is an island in the state of Massachusetts in the United States, about south of the Cape Cod peninsula. Together with the small islands of Tuckernuck Island, Tuckernuck and Muskeget Island, Muskeget, it constitutes the Town and Co ...

, Massachusetts, Martha's Vineyard, Massachusetts, Delaware beaches, northern Virginia beaches, the

Outer Banks The Outer Banks (frequently abbreviated OBX) are a string of barrier islands and spits off the coast of North Carolina and southeastern Virginia, on the east coast of the United States. They line most of the North Carolina coastline, separatin ...

of North Carolina to Santa Catarina, Brazil, on

Fernando de Noronha Fernando de Noronha (), officially the State District of Fernando de Noronha () and formerly known as the Federal Territory of Fernando de Noronha () until 1988, is an archipelago in the Atlantic Ocean, part of the state of Pernambuco, Brazil, and ...

, and

Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...

. Its

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic larvae have been documented in

Woods Hole, Massachusetts Woods Hole is a census-designated place in the town of Falmouth in Barnstable County, Massachusetts, United States. It lies at the extreme southwestern corner of Cape Cod, near Martha's Vineyard and the Elizabeth Islands. The population was 78 ...

, although the adults have not been recorded at this location.

Fossil record

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

specimens of ''O. quadrata'' have been found in rocks dating from the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

Ecology

Atlantic ghost crab of Rehoboth Beach 2020c

The Atlantic ghost crab lives in burrows in sand above the strandline. Older individuals dig their burrows farther from the sea, some starting as much as inland. Burrows can be up to deep, and can be closed off with sand during hot periods. This crab can produce a variety of sounds by striking the ground with the

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or Arthro ...

, by

stridulation Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fish, snakes and spiders. The mech ...

with the

legs A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element cap ...

, and an incompletely explained "bubbling sound". Males compete in a heavily ritualised manner which prevents the need for physical contact. Ghost crabs are arguably the fastest terrestrial invertebrates, capable of running at more than a meter per second. Studies on ''O. quadrata'' and its gonadal regions has revealed that, while the species can breed year-round, they have a tendency to be more active in their reproductive efforts during the summer months of the year. ''O. quadrata'' is more active at night than in the day, and is an

omnivore An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize t ...

, eating

clam Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams h ...

s (such as coquina clams and '' Donax'' spp.),

mole crab Hippoidea is a superfamily of decapod crustaceans known as mole crabs or sand crabs. Ecology Hippoids are adapted to burrowing into sandy beaches, a habit they share with raninid crabs, and the parallel evolution of the two groups is strikin ...

s (including '' Emerita talpoida''),

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s, plant material,

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

, and even other crabs. They also feed on the

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

s and

hatchling In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. A group of mammals called monotremes lay eggs, and their young are hatchlings as well. Fish Fish hatchlings generally do not receive parental care, similar t ...

s of

sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerh ...

s, such as the

loggerhead sea turtle The loggerhead sea turtle (''Caretta caretta'') is a species of sea turtle, oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the Family (biology), family Cheloniidae. The average loggerhead measures around ...

. Sandy beaches, a habitat frequented by ghost crabs, have had a decrease in the abundance of ghost crabs due to human behavior. Ghost crabs are negatively impacted by human and vehicle trampling, which results in direct crushing of crabs, as well as indirect damage such as compression of sediment which reduces habitat suitability, interference with reproductive behaviors, reduction in food supply, and

light pollution Light pollution is the presence of any unwanted, inappropriate, or excessive artificial Visible spectrum, lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting sources, during the ...

. Consequently, they may be less common on beaches frequented by people.

Self-awareness

A 2023 study using the well known

mirror test The mirror test—sometimes called the mark test, mirror self-recognition (MSR) test, red spot technique, or rouge test—is a behavioral technique developed in 1970 by American psychologist Gordon Gallup Jr. to determine whether an animal posse ...

found that these crabs seem to be capable of recognizing themselves in a mirror. The study's author concluded that the data indicate that the crabs have "a rudimentary form of self-awareness".

References

External links

* {{Portal bar, Crustaceans, Marine life Ocypodoidea Crabs of the Atlantic Ocean Fauna of Bermuda Crustaceans of the United States Crustaceans of the Dominican Republic Crustaceans described in 1787