World of Crabs

Land and Freshwater Crabs
Crabs are normally thought of as marine or aquatic animals, in the tropics, however, several families have adapted to living on land and in freshwater, challenging a niche dominated by more successful arthropods such as insect and spider.

Forest and Rice fields
This crab live in forest and some of them are adaptable and able to live around villages and cultivated areas in unpolluted drains and ricefield. Two of the most common in Java are Parathelphusaconvesa and Geosesama noduliferum.

Land Hermit and Robber Crabs
Land hermit crabs (Coenobita) and robber crab (Birgus latro) are the only genera in the family Coenobidae. Although they look very different, they are closely related. Land hermit crab carry a shell throughout their lives, whereas robber crabs only do so when they are young.

Land hermit crabs usually found closer to the sea than robber crabs. During the day, adults hide under vegetation in holes and crevices above the beach. At night they emerge to forage for food. They are primarily scavengers with a preference for vegetable matter and will occasionally climb trees and shrubs to look for fruit and seedlings.

Land Crabs
True land crabs (Gecarcinidae) are represented in Indonesia by two genera. Gecarcoidae and Cardisoma. The only Gecarcoidae species, the purple land crab (G. lalandii), it is about 10 cm in width and inhabits forest and hilly areas. It is common on small islands where it does not face competition from large mammals. One unusual aspect of this species behavior is the way both sexes march en masse to the sea to breed each year. When the larvae have completed their development at sea, they return to the beach and march inland to find food and safe resting places.

Crown Crabs
This crab are very small (often 0.5 to 1.0 centimeters in body width and feed on detrifus and small animals, usually in estuarine habitats. Some species have made their way into fresh water ecosystem. In Indonesia just two freshwater species are known, which is probably an underestimate of the actual number. One of these, the blind crown crab (Cancrocaeca xenomorpha) is one of the most unusual members of its genus, it lives within cave in Sulawesi, is totally blind and lacks pigmentation.

Light-foot CrabsLand and freshwater light-foot crabs (Grapsidae) are large-eyed crabs that are distinguished by their square shaped carapace. They are mainly herbivorous and are very agile on the ground, as well as on low trees. Unlike land crabs, Geosesarma species do not return to the sea to breed.