Coral Gall Crab – Hapalocarcinus marsupialis

The Coral Gall Crab – Hapalocarcinus marsupialis is a fascinating crustacean known for its unique symbiotic relationship with certain coral species. This crab is particularly well-adapted to its marine environment and plays a vital role in the health of coral reefs.

Description & Characteristics

The Hapalocarcinus marsupialis is characterized by its small size, typically reaching a maximum length of around 2 cm. Its body is flattened and somewhat heart-shaped, and it possesses a pair of prominent, elongated claws that are used for manipulating its environment and gathering food. The crab’s coloration varies depending on its habitat, often blending seamlessly with the surrounding coral.

Habitat and Occurrence

The Coral Gall Crab is found in a variety of marine environments, including the subtidal, sublittoral, infralittoral, and deep zones of the oceans. This species is common in the neritic zone, which extends from the lower limit of the intertidal zone to the shelf edge at approximately 200 meters water depth. The Hapalocarcinus marsupialis is a particularly prevalent inhabitant of coral reefs, where it forms a symbiotic relationship with certain coral species, specifically those in the genus Acropora.

Taxonomy

The species Hapalocarcinus marsupialis belongs to the Class: Malacostraca, Order: Decapoda, and Family: Cryptochiridae. This classification places it within the group of decapod crustaceans, which includes crabs, lobsters, and shrimp, and the family Cryptochiridae, which contains numerous species known for their close associations with corals and other marine invertebrates.

Feeding

The Coral Gall Crab is an opportunistic feeder, consuming a variety of organic matter, including mucus produced by its host coral, zooplankton, and small algae. Its diet is closely tied to the availability of food sources within its coral habitat. By consuming coral mucus, the Hapalocarcinus marsupialis plays a role in the health and maintenance of the coral, contributing to the overall stability of the reef ecosystem.