Ecology

Ghost crabs dig deep burrows near the intertidal zone of open sandy beaches. The burrows are usually composed of a long shaft with a chamber at the end, occasionally with a second entrance shaft. They are semi-terrestrial and breathe oxygen from the air through moistened gills. They must periodically wet their gills with seawater, usually by taking water from moist sand or by running into the surf and letting the waves wash over them. However, they can only remain under water for a limited amount of time, as they will drown.

Ghost crabs are generalists, scavenging carrion and debris, as well as preying on small animals, including sea turtle eggs and hatchlings, clams, and other crabs. They are predominantly nocturnal. They remain in their burrows during the hottest part of the day, and throughout the coldest part of the winter.

Ghost crabs are swift runners, darting away at the slightest sign of danger. They either head back to their burrows or plunge into the sea to escape intruders. The gaits of ghost crabs alter as their speed increases. Observations on O. ceratophthalma show it can walk indefinitely using all four pairs of walking legs, occasionally alternating which side leads. At higher speeds, the fourth pair of legs is raised off the ground, and at the highest speeds, the crab runs, using only the first and second pairs of walking legs.

Behavior

Ghost crabs generally look for food at night. This is also the time when they dig and repair their burrows. They search beaches for any animal or plant that has been washed ashore. It is rare to see these crabs during daytime as they are mainly active during night. Mature male ghost crabs neatly pile the burrowed sand next to their entrance. Young and female crabs do not make a eat pile and the sand they dig out is scattered in all directions beside their entrance. Female crabs can identify a male residence by the neat sand pile and get a mate for themselves. Younger crabs burrow and make homes in the area of shore that is closer to water. Older crabs are seen to burrow away from water.

Significance of presence of claws in the body of crab

Because there are both mutual and conflicting interests in most animal signaling systems, a central problem in signaling theory is dishonesty or cheating. For example, if foraging birds are safer when they give a warning call, cheats could give false alarms at random, just in case a predator is nearby. But too much cheating could cause the signaling system to collapse. Every dishonest signal weakens the integrity of the signaling system, and so reduces the fitness of the group. An example of dishonest signaling comes from Fiddler crabs such as Uca lactea mjoebergi, which have been shown to bluff (no conscious intention being implied) about their fighting ability. When a claw is lost, a crab occasionally regrows a weaker claw that nevertheless intimidates crabs with smaller but stronger claws. The proportion of dishonest signals is low enough for it not to be worthwhile for crabs to test the honesty of every signal through combat.

 Because the claw muscles of crustaceans – which underpin their fighting capacity – are cryptically concealed beneath an exoskeleton, it is difficult for competitors to accurately assess the strength of their opponents without physical contact. This allows for the potential decoupling of weapon size and underlying ability, enabling individuals to display large weaponry without necessarily having the strength to match their signals .As such, unreliable signalers could gain access to resources by deceiving opponents, and may also save substantial energy by developing less muscle and by reducing the cost of its ongoing maintenance.

CRABS ARE CHOSEN FOR THEIR FAUNAL STUDY BECAUSE,

1. Firstly they are amphibians i.e. they can adapt to both water and land environment.

2. Secondly due to intermediate and variable climate prevailing in the sea beaches, these crustaceans are abundant over all the other faunal species other than fishes which are exclusively marine in nature.

3. Thirdly, crab behavior is more suitable an easier to study than other faunal behavior patterns because of their quick visual concept against a particular subject.

Tajpur beach has three species of crab present abundantly.

1 FIDDLER CRAB :-A fiddler crab, sometimes known as a calling crab, may be any of approximately 100 species of semi-terrestrial marine crabs which make up the genus Uca.  As members of the family Ocypodidae, fiddler crabs are most closely related to the ghost crabs of the genus Ocypode.

2 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 predators of small animals. The name "ghost crab" derives from their nocturnality and their generally pale coloration. They are also sometimes called sand crabs, though the name refers to various other crabs that do not belong to the subfamily.

3 TOTTILA CRAB

They are the smallest of all the three.