| Gecarcinus ruricola | |
|---|---|
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| Infraorder: | Brachyura |
| Family: | Gecarcinidae |
| Genus: | Gecarcinus |
| Species: | G. ruricola |
| Binomial name | |
| Gecarcinus ruricola | |
| Synonyms [2] | |
| |
Gecarcinus ruricola is aspecies ofterrestrial crab. It is the most terrestrial of theCaribbean land crabs,[3] and is found from westernCuba across theAntilles as far east asBarbados. Common names forG. ruricola include thepurple land crab,[1]black land crab,[3]red land crab,[4] andzombie crab.[5]
Four colour morphs exist within the species - black, red, yellow, and green. Thecarapace ofG. ruricola grows in width at a rate of about 1 in (25 mm) per year, with the crabs reaching maturity after 5 years, and living for up to 10 years in total.[6]G. ruricola crabs have a number ofadaptations to terrestrial life, mostly regardingwater conservation. They are nocturnal, to prevent the hot sun from drying them out. They also have a "nephritic pad", onto whichurine is released, to be cleaned bymicrobes before the water is then reabsorbed.[7]
G. ruricola is found across much of theCaribbean, from Cuba and theBahamas in the west through the Antilles to Barbados in the east. It has been reported fromFlorida andNicaragua, but few confirmed examples exist from the mainland;Loggerhead Key in theDry Tortugas marks the northernmost limit of its island distribution, which extends across the Bahamas and Cuba, through the Greater and Lesser Antilles, to Barbados. Outlying populations exist onCuraçao, in theSwan Islands offHonduras, Half Moon Caye of Belize, and theArchipelago of San Andrés, Providencia and Santa Catalina off theColombian coast.[3]
It can be found at great distances from the sea, and at highaltitudes; it has been observed above 300 m (980 ft) on the island ofDominica, and at over 1,000 m (3,300 ft) onJamaica.[3]
Theeggs ofG. ruricola hatch in the sea,[6] where thelarvae live asplankton. The return of the larvae to land seems to be infrequent, but when they do return, they return asmegalopa larvae, in sufficient numbers to turn roads red.[8] They move at speeds of 1–2 m/s (2.2–4.5 mph), or faster if startled.[9] For the next three years, the young crabs live inburrows inhabited by other crabs, and eat food brought back to the burrow by the older crab.[6]
After mating, massmigrations occur, with the females returning to the sea to release their fertilised eggs. A typical female carries around 85,000 eggs.[8]
G. ruricola is anomnivorousscavenger,[6] feeding mostly onnitrogen-poor plant matter.[8]
The meat ofG. ruricola is rich inprotein, and has often been harvested by local people. Otherpredators may includebirds, although information is scarce. When confronted, they rear up and hold their open claws outwards in a defensive posture.[6]
G. ruricola is thehost organism for two species ofcommensalflies in the genusDrosophila.[10] They were first observed onMontserrat byHenry Guernsey Hubbard in 1894, and presented at ascientific meeting later that year (where the crab was misidentified asCardisoma guanhumi), but no further research was conducted until 1955, when specimens were again collected, this time fromMona Island, and named asDrosophila carcinophila by M. R. Wheeler.[11]
In 1967, a second species of fly,Drosophila endobranchia, was discovered onG. ruricola, although it also inhabits the closely related speciesG. lateralis.D. endrobranchia is not closely related toD. carcinophila, and this trait appears to haveevolved convergently. (A third species of fly,Lissocephala powelli, has evolved a similar habit onChristmas Island, where it lives on the land crabsGecarcoidea lalandii,Geograpsus crinipes, andCardisoma carnifex, and the terrestrialhermit crabBirgus latro.)D. endobranchia evolved from a group of species that breeds on fungi or bark, whileD. carcinophila evolved from a group that breeds oncacti.[10]
The flies spend most of their lives on the crab, and are reluctant to leave. They do not need to flee predators, because the crabs they inhabit are fast animals and will flee:[7]
The flies … hardly move at all, are extremely reluctant in leaving their host crabs and are hard pushed to take flight. Although the flies are sluggish, the crabs on which they reside are anything but. Chasing after crabs through a pitch-black jungle (growing on a razor-sharp labyrinthine limestone ground), while trying to aspirate flies from their carapaces is not trivial. Obtaining large amounts of flies in this way is simply a nightmare.
Theeggs are laid around the crab'scompound eyes; the first-instarlarvae migrate to the crab's nephritic pad, and live there, feeding on the microbes that cleanse the crab's urine. The second instar is spent in the crab'sgill chamber. The third instar has the larvae return to themouthparts before falling to the ground topupate.[7]
Carl Linnaeus described the species in 1758 (the starting point forzoological nomenclature), noting the species' annual migrations from the forests to the coast (Habitat in America, sylvas vastissimis agminibus quotannis deserens littora maris petiturus: "lives in America; every year, an army marches out of the forests towards the seashore").[12]
G. ruricola appeared on twoAfricanpostage stamps for theInternational Year of the Ocean in 1998, under the name "mountain crab". These were aTanzanian stamp worthTSh 500/= and aUgandan stamp worthUSh 250/=.[13]
