Scientific Name : Ocypode ceratophthalmus
Common Name : Horned Ghost Crab or Horn-eyed Ghost Crab
Place : Gertak Sanggul
Date : 09.10.2010
Scientific Classification | |
| | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Crustacea |
| Class: | Malacostraca |
| Order: |
Decapoda |
| Infraorder: | Brachyura |
| Family: | Ocypodidae |
| Genus: | Ocypode |
| Species: | O.ceratophthalmus |
General Description about Ghost Crab
Ghost crabs, also called sand crabs, are crabs of the genus Ocypode, common shore crabs in many countries. Characteristics of the genus include one claw being larger than the other.
These crabs are called ghosts because they are translucent, and because of their ability to disappear from sight almost instantly, scuttling at speeds up to 10 miles per hour, while making sharp directional changes. These creatures have two black eyes, with very good 360° vision. The ghost crab tunnels down four feet into the ground at a 45° angle, creating 1–2 inches (25–51 mm) wide holes, which speckle the beach. You might notice the golfball-sized entrance holes of the Ghost Crab burrows in the dry sand of the upper beach, or in the sand dunes. The burrows extend down 3-4 feet. The “Ghostie” brings up clawful of sand and tosses them 6-12 inches away from the burrow opening. Later on, the Ghost Crab tromps down the strewn-about sand, and, using its claws, smooth out the surface. Another entrance style is represented by a dome of sand which covers the burrow hole. At dusk, these crabs will sprint to the ocean in order to obtain oxygen from the water which washes over their gills, and in the beginning of the summer, females will release their eggs into the ocean.
Description about Ocypode ceratophthalmus
Ocypode ceratophthalmus, the horned ghost crab or horn-eyed ghost crab, is a species of ghost crab. It lives in the Indo-Pacific region from East Africa to the Philippines and the Great Barrier Reef. They are sand-colored and somewhat diaphanous. Horned Ghost crabs can be distinguished from other related crabs by the eyestalks extending beyond the eyes into long points, which are longer in males, and shorter in females and juveniles. The crabs have a box-shaped body, 6–8 centimetres (2.4–3.1 inches) across the carapace, with a darker marking towards the rear in the shape of an H.
Horned Ghost crabs have eight walking legs which are on the backside of the crab’s body make the crab walk either right or left. One side of the four back legs helps pull the crab, and the other side stretches out and push. The crab usually does not move straight forward. Horned Ghost crabs can really run fast, as suggested by their scientific name ("Ocy" means swift and "podi" foot in Greek). They literally fly over the sand and their movement has been described as a small leaf blowing over the sand surface. In fact, they may be among the fastest land creatures, moving at 100 bodylengths per second. In comparison, the cockroach does 50 bodylengths while the cheetah does a sluggish 10 bodylengths. Horned Ghost crabs are only beaten by tiger beetles which do 171 body lengths when they are really scared. Being fast moving creatures, Horned Ghost crabs have excellent eyesight to see where they are going. Their eyes are on stalks. Horned Ghost crabs can run at speeds of up to 2.1 metres per second (6.9 ft/s). Their stalked black eyes give them an extraterrestrial appearance, and they scurry about in a rather purposeful manner. You will probably only see them at dusk or at night.
The Horned Ghost crabs are well adapted for life out of water and are among the few marine creatures that roam the beaches at low tide. They can stay for a long time away from the sea because they can absorb water from the wet sand through special hairs on the base of their legs by capillary action.
Horned Ghost crabs live in burrows that they dig high up on the shore away from the water. It is said that when tunneling out their burrow, they carry sand to about 50-100 cm away from their burrow entrance, then toss the sand as far as they can. This behavior probably explains the typical "spray" pattern of sand around their burrow.
Anatomy
A Horned Ghost crab has three main parts on its body. It is hard to see those parts if you look at the crab from above. You have to flip the crab over to see the parts because the carapace covers it. A carapace is the main part of the body where the shell is hard. Its head and the middle part of the body are called the thorax. The cephalothorax is what joins the head and the middle section together. The legs are mostly used for transportation. The front two legs of the crab are the closest to its head. They are sometimes used for walking but mostly used for eating. Those two legs are called chelipeds. The claw/pincher on the cheliped is called chela. The chelas are used to grasp or hold something. The pinching part located on the front of the crab’s body is the claws. The claws help the crabs catch their prey. Sometime crabs get so scared of humans that when they pinch the person their claw breaks off. Soon after a claw breaks off, a new one will grow on. Crabs have a soft inner layer and a hard outer layer. Animals with this type of body are also known as crustaceans. Crustaceans are also known as decapods. Decapods are 10-footed animals. Other decapods are lobsters and shrimp.
Life Cycle
Females with egg masses need to frequently enter the water to keep the eggs wet. Although Ghost Crabs cannot swim, the females may turn upside down in the water to ventilate the egg mass which is carried under her tail. The babies begin life in the water, and then become amphibious temporally.
When the female crab has baby crabs, they come out in eggs. When the female crab lays her eggs, she puts them in water. Then she moves fast above the eggs, so that they will hatch. When the baby crabs hatch, they are called larvae. They do not look at all like the adult crabs. They have to go through stages of their life before they look like a crab. During the first stage, the crab is known as a zoea. The zoea is very tiny and looks a lot like a shrimp. When the crab is a zoea, it is usually about 1 millimeter (1/ 25 inches) long. The zoea usually feeds only on the larvae of oysters and starfish. The zoea starts to shed the outer layer of its shell because it is getting big. This is called molting.
When the crab enters its second stage of growing it is called megalops. This means that it has large eyes. The megalops also gets its claws and the appendages of an adult crab. This shows that the crab is almost done growing.
During the final stage, the crabs are full grown. The megalops on the crab molts. Then a young crab has all of the body parts that an adult crab has. The hard part that gets made during this process is called a chitin. A chitin is the hard part of the crab also known as a carapace. When the crab grows, the chitin grows with it. The chitin stays with the crab for its whole life.
Role in the Food Chain
Horned Ghost crabs are scavengers, foraging at night for any dead creatures left behind on the shore at low tide. They may also hunt small animals and clams and snails near the water's edge. At night, they have been seen foraging on the wet intertidal near the mid-water mark. Horned Ghost Crabs scavenge the beach, looking for tasty things to eat. Once a year, when baby sea turtles are hatching out, they enjoy special feasts. They drag the three-inch-long hatchlings down into their underground burrows, and devour them.
Besides eating baby sea turtles, the Horned Ghost Crab likes beach fleas, coquina clams, mole crabs, lizards, and carrion. It feeds at night. Ghost crabs deal with the dead in their habitat.
Horned Ghost crabs are in turn eaten by many animals higher up in the food chain. On some of the Caribbean Islands, Ghost Crabs are a human food source. Like other creatures of the intertidal zone, Ghost crabs are affected by human activities such as reclamation and pollution. Trampling by careless visitors also has an impact on local populations.
