Blue-legged hermit crab

Lore & Background

Clibanarius tricolor has blue legs with red banding between each segment, reaching up to 2 centimeters in size. Males are larger than females, as is typical for most hermit crab species. It lives in shallow waters of the Caribbean Sea, often congregating in rocky areas with about 30 centimeters of water. During the day, the crabs move slowly or rest, with feeding beginning at dusk and continuing through the night. Members of the same group tend to move in one general direction while feeding, similar to grazing cattle, and return to their congregation by 4:30 in the morning. Most crabs stay with the same respective groups day after day. Shell fighting occurs in this species. An attacking crab approaches from behind, turns the victim on its back, and may spin both crab and shell multiple times. The attacker raises its own shell and brings it down rapidly, repeating the process until it kicks the victim out of the shell. If the attack fails, the victim may remain upside down and face another attack.

Reader's Guide

Clibanarius tricolor is a detritivore that consumes dead plants and animals, preventing debris from clogging the reef. It also eats green hair algae, cyanobacteria, and seaweed, and sifts through sand to find food, thereby cleaning the sand. This feeding behavior makes it a valuable member of the reef ecosystem and a popular aquarium species. In the home aquarium, its coloration and cleaning habits have made it emblematic of a shift from purely decorative animals to 'working' animals that help sustain the aquarium's ecosystem, reducing the need for active management by the owner. The crabs are most active at night, feeding from dusk until early morning, and they tend to remain in stable social groups within rocky areas of shallow water.

Did You Know?

• Males are larger than females.
• It feeds at dusk and continues through the night.
• Shell fighting involves the attacker turning the victim on its back and spinning it.