The Caribbean king crab, also known as the Caribbean king crab, is an impressive crab that lives in the tropical waters of the western Atlantic and ranks among the largest reef crabs in the Caribbean. Despite its spectacular appearance, with a shell covered in tubercles and spines, this reef giant often spends the day sheltered in crevices or beneath rocky overhangs. It nevertheless plays an important role in the ecosystem by consuming large quantities of algae that can compete with corals.

The Caribbean king crab has a broad, rounded carapace that is slightly narrower toward the front, generally reddish brown to dark red with yellowish hues. Its surface is covered with numerous tubercles and large spines, while its long legs also bear numerous bumps and projections. The rostrum, located at the front of the carapace, is very short and deeply notched. Adult males are particularly large, and the largest individuals can have a carapace more than 7.5 inches wide.

Its two claws are relatively similar in size, unlike those of many other crabs in which one claw is noticeably more developed than the other. The claws of males are nevertheless more robust than those of females.

The Caribbean king crab inhabits the tropical and subtropical waters of the western North Atlantic, from Florida and the Bahamas throughout the Caribbean, including Guadeloupe, Martinique, and Saint Barthélemy, south to Venezuela, as well as the Gulf of Mexico.

The Caribbean king crab primarily inhabits rocky bottoms and coral reefs with abundant crevices and shelter. It seeks out cracks, cavities, and the undersides of overhangs where it can remain hidden during the day. It occurs in both shallow waters and depths of more than 330 feet.

The Caribbean king crab is primarily herbivorous. It grazes on a wide variety of algae that cover rocks and reefs. It can notably consume species of algae that some fish and other herbivores avoid because of their deterrent compounds or texture.

Its diet is not exclusively plant-based, however. It can also opportunistically consume small benthic organisms, carrion, and debris. By consuming large quantities of algae, it therefore helps limit their growth on reefs.

Like other crabs, the Caribbean king crab reproduces by mating, after which the female carries the eggs beneath her abdomen until they hatch. When they hatch, young crabs first go through several developmental stages in the open water before gradually transforming into small crabs capable of living on the seafloor.

This relatively short developmental phase has attracted scientific interest in the semi-intensive rearing of this species in its natural environment, with the aim of contributing to coral reef restoration.

Studies conducted in the Florida Keys on the semi-intensive rearing of Caribbean king crabs for coral reef restoration have shown that by consuming large quantities of algae, they help limit its growth and leave more space for corals, thereby promoting their growth on reefs.