The ghost crabs or sand crabs are semi-terrestrial decapod crustaceans belonging to the Ocypodinae subfamily. They are mainly white in color, although they can vary it to camouflage with their surroundings.
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Brief Overview of the Ghost Crabs
First described in 1860, the ghostcrabs have remained on our planet virtually unchanged since the Quaternary era, after the disappearance of the dinosaurs, evolving along with the first humans. Their presence is considered an indicator of healthy beaches, since they are particularly sensitive to chemical pollutants such as oil derivatives.
However, the main danger they face in tourist places relies in the destruction of their habitats by urbanization and the continuous walk of people, which prevents them from eating and build their underground dens.
These crabs are characterized by having one claw larger than the other. However, this feature is not as marked as in the case of the male fiddler crabs . The subfamily Ocypodinae includes twenty two species in two genera, and belongs to the family Ocypodidae where the taxon of fiddler crabs (Ucinae) is also enclosed.
Ghost Crabs’ Anatomy
There is a wide variety of ghost crabs, so depending on the species may differ in their general characteristics. Their sizes range from a few millimeters, up to four meters wide when their legs are extended. Most ghost crabs have pale colored bodies, although they are able to gradually change that color to match their surroundings and the time of day. Some species are even of bright colors, such as the Ocypode gaudichaudii and Ocypode ryderi.
These decapods have a thick exoskeleton composed of highly mineralized chitin, four pairs of legs, a pair of claws and elongated and swollen peduncles that can swivel 360 degrees.
Their carapaces are usually deep and have a square shape. The types of ghost crabs can be identified more easily by means of the area where they are found. We can mention the O. quadratus, which inhabits the western Atlantic coast from New Jersey to Brazil, the O. ceratophthalmus, found on the beaches of the Indian and Pacific oceans and the ghost crab O. saratan, belonging to the Red Sea.
Other distinctive features of the Ghost Crabs
The ghost crabs emit a unique bubbling sound when they strike with their claws on the ground and rub their legs. Their scientific name, Ocypode means «fast feet», since they often move at a speed of up to 10 miles per hour.
When the ghost crabs breathe oxygen, they need to keep their gills wet, so it is common to see them ingesting seawater or absorbing moisture from wet sand. As for their diet, it consists mainly of sea turtle hatchlings, turtle eggs, clams, insects and other crabs.
Now…. let´s watch them
Common Habitats of the Ghost Crabs
The ghost crabs live in small burrows in the sand, preferring a solitary life with only one crab per burrow. These places are commonly dug at a 45-degree angle and can be up to 1.5 meters deep. They create their burrows with angled entrances so that the breeze blows in them, allowing the ghost crabs to be ventilated.
Ghost Crabs Reproductive Method
The ghost crabs, like most crabs, depend on the sea to perpetuate their species. During mating, the male ghost crab deposits its «genetic material» on the female, holding its claws tightly. After a quick and unpleasant encounter with the male, the female is released and fled to her burrow, maturing her eggs in her body and depositing them shortly after in the sea, which will later return in the form of larvae and live buried in the sand until they reach their adulthood.
An interesting feature of these crabs relies on their huge appetite, which makes them very territorial and not very tolerant with other crabs. From time to time they must dispute their food among themselves, which makes them fight and use their powerful pincers. There are rarely deadly duels, but it is very common for them to lose a leg or a pincer during the fight.
Fortunately, they can recover such limb when they molt their exoskeleton. Since this is an external structure it just can´t grow, so the ghost crabs ( as most crabs)periodically grow a new one underneath, discarding the old one and growing a little more while the new «exoskeleton» hardens. Unfortunately for them, that exoskeleton is not hard enough to withstand the stomp of a scared or distracted tourist.
let´s have a final look of them