Ryan Photographic - Ocypodidae - Ghost and fiddler crabs
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Family Ocypodidae
There are currently 129 species of ocypodid crabs classified into 14 genera. The family was subjected to major revision in 2016 by Hsi-Te Shih et al. who carried out nuclear and mitochondrial DNA analysis to produce a comprehensive understanding of relationships.
The ghost crab ocypodids live in the intertidal of tropical and sub-tropical waters where they inhabit burrows while the tide is in and emerge at low tide to forage. The ghost crabs are fast-moving. When threatened they will make for their burrow but if intercepted move seawards and attempt to bury themselves. Both sexes may possess stridulating ridges on the inside of their big claw. I assume they rub this against their carapace to produce sound but I have been unable to verify this (mostly because the articles I need to read are protected by publishers - they only wanted 51 British pounds for one reprint - pack of money-gouging children of unmarried parents). In one species it has been determined that the crab will stridulate to warn off potential predators or rivals until they are very close. At this point the crab switches to noise production via its gastric mill where internal teeth produce noise. This frees up the major claw for defense.
Ghost crabs are able to change their color to match backgrounds, but this is not a fast process. The species with which I am most familiar, Ocypode cerathopthalma, becomes darker at night.
The fiddler crabs, so called because the males possess an enlarged chela with which they signal females and therefore appear to be "fiddling" (as in playing the fiddle) are also widely distributed. Some of them are very brightly colored, thereby providing a splash of color in their otherwise typically monotone landscapes. There may be several different species in the same area and they usually have different colored claws and wave them in a species specific pattern - all designed to lure a lady friend into their burrow. Conflicts between males are common. Typically a burrow owner is able to defend it, but every now and then the intruder wins.
Austruca lactea
Austruca lactea, male, Buca Bay, Vanua Levu, Fiji IMG_0266
Austruca perplexa Fiddler crab
Austruca perplexa Fiji
Gelasimus excisa fiddler crab
Gelasimus excisa fiddler crab, Nagura Amparu Ramsar wetland site, Ishigaki Island IMG_0170
Gelasimus tetragonon Fiddler crab
Gelasimus tetragonon, Sulawesi, full frontal
Gelasimus tetragonon, Sulawesi
Gelasimus vocans
Gelasimus vocans Yellow hand fiddler crab Sulawesi, Indonesia
Minuca rapax Atlantic marsh fiddler crab
Minuca rapax Atlantic marsh fiddler crab, Mississippi Delta IMG_0040
Ocypode cerathopthalma ghost crab
Ocypode cerathopthalma ghost crab, male 3, Fiji
Ocypode cerathopthalma Ghost crab male 2, Fiji
Ocypode cerathopthalma Ghost crab, Fiji male eyes
Ocypode cerathopthalma Ghost crab male at night, Fiji
Ocypode cerathopthalma Ghost crab female, Fiji 5
Ocypode cerathopthalma ghost crab female 4, Fiji
Ocypode cerathopthalma Ghost crab female, Fiji 3
Ocypode cerathopthalma Ghost crab female 2 Fiji
Ocypode cerathopthalma Ghost crab female 2 Fiji
Ocypode cordimana Little ghost crab
Ocypode cordimana little ghost crab 2 Fiji
Ocypode cordimana little ghost crab 2 Fiji
Paraleptuca crassipes Scarlet fiddler crab Sulawesi
Paraleptuca crassipes Scarlet fiddler crab Sulawesi
Tubuca coarctata Fiddler crab
Tubuca coarctata fiddler crabs fighting, Naisoso, Nadi, Fiji IMG_0232
Tubuca coarctata, male and female, Naisoso, Fiji IMG_0284
Tubuca dussumieri Dussumier's fiddler crab
Tubuca dussumieri
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