The Rusty Guard Crab, Two Tooth Guard Crab or Trapezia bidentata is a fascinating species of crab known for its vibrant coloration and commensal relationship with corals. This unique crab is found in tropical regions of the Indo-Pacific, playing a crucial role in the intricate web of life within coral reefs.
Description & Characteristics
The Trapezia bidentata is easily recognized by its distinctive rusty-brown to reddish-brown carapace, or shell. This coloration provides camouflage amidst the coral environment. The crab’s carapace can reach a maximum size of approximately 3 centimeters in width, although it typically remains smaller. The Trapezia bidentata also has two prominent teeth on its front edge, hence its common name “Two Tooth Guard Crab”.
Habitat and Occurrence
The Rusty Guard Crab, Two Tooth Guard Crab is an integral part of coral reef ecosystems. It is primarily found in the Indo-Pacific region, residing in both the inner and outer reef zones. This crab prefers shallow, warm waters with ample coral cover, where it can establish a symbiotic relationship with its host coral. They are typically found in depths ranging from the intertidal zone to approximately 30 meters.
Taxonomy
The species Trapezia bidentata belongs to the Trapeziidae family, which is part of the Decapoda order, belonging to the Malacostraca class. This classification reflects the crab’s characteristics as a decapod crustacean with ten legs.
Feeding
The Rusty Guard Crab, Two Tooth Guard Crab is a carnivore, feeding primarily on zooplankton and other small invertebrates. Its diet also includes mucus produced by its host coral, which it scrapes off the coral surface. This commensalistic relationship benefits both the crab and the coral. The crab gains a safe and stable habitat, while the coral benefits from the crab’s removal of parasites and algae.
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