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Caribbean king crab

Mithrax spinosissimus

Today's Research for Tomorrow's Oceans

Species Type:


Common Name(s):

Caribbean king crab


The carapace, or shell, of a Caribbean king crab is around 5.4 inches (136 millimeters) for males and 4.7 inches (120 millimeters) for females. They can weigh up to 6 pounds (3 Kilograms).


Masters at foraging, Caribbean king crabs are herbivorous and eat the algae growing on coral reefs. This is beneficial to the reef because it'll keep the algae from preventing coral growth and throwing off the bacterial make up of the community.

Range & Habitat:

Caves and shallow reef communities anywhere from North Carolina down to Venezuela is where the Caribbean king crab likes to live.


Caribbean king crabs are highly adaptable invertebrates and are able to live in polar or temperate aquatic ecosystems. This species of crab is helping coral reef communities battle environmental stressors caused by human activity. As excellent grazers, Caribbean king crabs help combat algae overgrowth fueled by pollution, overfishing and climate change. These social crabs are very protective of their own kind and will lend a claw if another crab is being bothered by a predator.