Trapezia (genus)

Trapezia is a genus of crabs in the family Trapeziidae. These small crabs are commonly found living symbiotically within corals, particularly Pocillopora and other branching stony corals. They are obligate symbionts, meaning they cannot survive without their coral host.

Trapezia crabs are characterized by their distinct trapezoidal carapace (the dorsal section of their exoskeleton), from which the genus name is derived. The shape, size, and coloration can vary considerably between species. They are typically brightly colored, often displaying patterns of red, orange, yellow, or brown.

The symbiotic relationship between Trapezia crabs and their coral hosts is mutualistic. The crabs defend the coral from predators, such as crown-of-thorns starfish and other coral-eating organisms. In return, the coral provides the crabs with shelter and a food source, primarily mucus secreted by the coral. The crabs also graze on algae and detritus that accumulate on the coral surface.

Trapezia crabs play a vital role in maintaining the health and resilience of coral reefs. Their defensive behavior helps to protect corals from damage and disease, contributing to the overall biodiversity and stability of these important ecosystems.