The gulf ghost crab, ''Hoplocypode occidentalis'', is a species of ghost crabs native to the Pacific 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 ...

, from the Gulf of California to

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

. It is the only species in the genus ''Hoplocypode''. Gulf ghost crabs are medium-sized, reaching a maximum overall body diameter of . They are one of only two ghost crab species found in the eastern Pacific (the other being the painted ghost crabs). However, gulf ghost crabs can easily be distinguished from painted ghost crabs by the absence of "horns" on their eyes.

Taxonomy

''Hoplocypode occidentalis'' was first described by the American marine biologist William Stimpson in 1860 as ''Ocypoda occidentalis''. The type specimens were originally collected from

Cabo San Lucas Cabo San Lucas (, "Saint Luke Cape"), or simply just Cabo, is a resort city at the southern tip of the Baja California Peninsula, in the Mexican state of Baja California Sur. As at the 2020 Census, the population of the city was 202,694 inhabitan ...

, Baja California, Mexico. It was transferred to its own genus ''Hoplocypode'' in 2013 by Katsushi Sakai and Michael Türkay based on the differences of their gonopods (appendages modified into copulatory organs) from that of the rest of the members of the genus '' Ocypode''. It is classified under the ghost crab

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

Ocypodinae in the family Ocypodidae. The specific name is from Latin ''

occidentalis This list of Latin and Greek words commonly used in systematic names is intended to help those unfamiliar with classical languages to understand and remember the scientific names of organisms. The binomial nomenclature used for animals and plants i ...

'' ("western"). They are commonly known as the "gulf ghost crab" in English and ''cangrejo de playa'' in Spanish.

Description

Gulf ghost crabs are medium-sized ghost crabs with deep bodies, reaching a maximum overall body diameter of . The upper surface of the body is generally dark gray with lighter colored marbling. The underside of the body, the tips of the walking legs, and the claws are creamy white. Their coloration varies, usually matching the color of the sand surrounding them, but they are easier to see on black volcanic sand and on light-colored dry sand. Hoplocypode leg

The carapace is squarish in shape and wider than it is long, with a length around and a width of . It is thickly covered with rough, small bumps (tubercles). Their eyestalks are large and elongated, but do not possess "horns" as in some other ghost crab species. The outer half of margins of the eye sockets curve distinctly inwards, with the outer edges (exorbital angles) triangular in shape with a sharp, forward-facing, pointed end. Like other ghost crabs, one of the claw appendages ( chelipeds, the first

pereiopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

pair) of gulf ghost crabs is much bigger than the other. The palm of the larger cheliped is elongated with a serrated lower edge and covered with tubercles on the upper surface. It features

stridulating 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 ...

(sound-producing) ridges on the inner surface of the palm, which is important for identifying different species within the subfamily Ocypodinae. In gulf ghost crabs, the stridulating ridge is short and composed of a row of 21 to 22 tubercles. The smaller cheliped tapers towards a pointed end. The second pair of walking legs are not more than two and a half times the length of the carapace. The fourth pair is relatively smaller and weaker in comparison to the other three pairs, reaching only to the middle of the propodus of the third pair. The mera and

carpi Carpi may refer to: Places * Carpi, Emilia-Romagna, a large town in the province of Modena, central Italy * Carpi (Africa), a city and former diocese of Roman Africa, now a Latin Catholic titular bishopric People * Carpi (people), an ancie ...

of all the legs are naked, but the propodi possess fur-like bristles (setae) on for the first three walking leg pairs varying by sex. In males, the propodi of the first and second pair of walking legs have their upper forward surfaces covered with setae. The propodi of the third pair of walking legs only have setae on the upper margin of the propodi. In females, the propodi of the third and last pair of walking legs do not possess bristles on the upper surfaces of their propodi. The first gonopods (modified copulatory organs) of males are also distinctively complex in shape, with a triangular cross-section at the base and becoming hoof-like towards the end. This characteristic is one of the diagnostic criteria for the genus. The covering (operculum) of the genital duct of the females has four sides and is membranous and slightly calcified. The genital slit is narrow and aligned along the middle of the operculum.

Ecology

Gulf ghost crabs live in burrows near the

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...

of open sandy beaches and on sand and silt banks near where river mouths empty into the sea. Larger individuals usually have burrows further up the shore, while smaller individuals are closer to the waves. They are

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

, emerging from their burrows just after sunset. They are fast-moving generalist

scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...

s and predators, usually feeding on decaying bodies of fish and other

crustacea Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean gro ...

ns. They are also devastating predators of eggs and hatchlings of sea turtles, including the olive Ridley sea turtle ('' Lepidochelys olivacea'') and the leatherback sea turtle ('' Dermochelys coriacea''). In Playa Grande, Costa Rica, they've been observed to be responsible for as much as 48% of the total number of deaths in freshly hatched sea turtles crossing the beaches towards the water.

Distribution

Gulf ghost crabs are native to the eastern Pacific coast of the Americas, from the Gulf of California to

. They are

sympatric In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...

with the painted ghost crab ('' Ocypode gaudichaudii''), and juvenile specimens of the two smaller than are very difficult to tell apart. However, the adults are readily distinguishable, as painted ghost crabs are brightly colored and possess "horns" (styles) on their eyestalks which are absent in gulf ghost crabs. Painted ghost crabs also prefer sheltered rocky beaches, while gulf coast crabs are found on open sandy beaches. Gulf ghost crabs also superficially resemble the Atlantic ghost crab (''

Ocypode quadrata The Atlantic ghost crab, ''Ocypode quadrata'', is a species of ghost crab. It is a common species along the Atlantic coast of the United States, where it is the only species of ghost crab; its range of distribution extends from its northernmost re ...

''), but the two species do not occur in the same areas, with the latter being only found in the western Atlantic coast of the Americas.

References

External links