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Horseshoe crab

Horseshoe Crab

Limulus polyphemus

The horseshoe crab is a living fossil with a dark brown, hinged protective shell and long tail, called a telson. The telson is harmless—the animal uses its tail to flip over if it becomes overturned by a wave. The horseshoe crab has 10 eyes scattered throughout its body and a number of additional light receptors near its tail.

On its underside, the horseshoe crab has a mouth surrounded by bristles, which are used to chew food. It has six pairs of jointed legs and six leather-like flaps, called book gills, which are used for breathing and swimming. The horseshoe crab’s brain is located in a thin circle around its mouth.

In the late spring and early summer, you may spot two or more horseshoe crabs hooked together. Special claws allow males to clasp onto a female’s shell and hitch a ride to the water’s edge where the female lays her eggs in the sand.

Did You Know?

The horseshoe crab may look like a crustacean but is actually more closely related to spiders and scorpions!


The horseshoe crab feeds on worms, small clams, dead fish and other organic materials.


Female horseshoe crabs average about 18-19 inches from head to tail, while males are slightly smaller reaching only about 14-15 inches.


The horseshoe crab is found along the North American Atlantic coast from as far north as Nova Scotia to Mexico’s Yucatan Peninsula.

Population Status

The horseshoe crab is considered near-threatened by the IUCN.


Many migrating shorebirds feed on horseshoe crabs during their spawning season. Other birds, reptiles and fish feed on horseshoe crab eggs. Humans are also a predator of horseshoe crabs, harvesting them for bait.

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