Horseshoe Crab, a marine arthropod that lives in shallow water. It is also called king crab and helmet crab. It is not a true crab because it has a soft and unsegmented abdomen. It has a horseshoe-shaped carapace (shell) and a spikelike tail. Its eyes are located on the outer edges of the carapace. Six pairs of legs are used for burrowing, swimming, crawling, and catching worms and shellfish, its main sources of food. The female lays eggs on the beach in early summer, and the young hatch in about six weeks.

There are four species of horseshoe crabs, three of them found in Asia and the other in North America. The North American horseshoe crab is about two feet (60 cm) long and one foot (30 cm) wide, and is greenish tan.

The eyes of horseshoe crabs are similar in anatomy to those of humans, and their blood is similar in composition. For these reasons, horseshoe crabs have been used in research on vision and blood clotting.

Horseshoe crabsHorseshoe crabs are large marine arthropods with six pairs of legs.
Are Horseshoe Crabs Crustaceans?

They have a hard, wide shell. They live on the seabed. And their name includes the word “crab.” But horseshoe crabs are neither crustaceans nor crabs. They actually are more closely related to scorpions and spiders.

Several differences separate the horseshoe crab from true crabs. True crabs have antennae, but horseshoe crabs do not. True crabs have 8 walking legs, plus 2 claws, whereas, horseshoe crabs have 10 walking legs.

Horseshoe crabs are not, however, totally unrelated to crabs. Scientists classify such crustaceans as true crabs, as well as horseshoe crabs, into a larger group of animals known as Arthropoda. Arthropods are animals with jointed legs, an exoskeleton made of chitin, and bodies that are divided into sections. Insects, crustaceans, spiders, and horseshoe crabs are all arthropods. In fact, about two-thirds of all the species of animals on the planet are arthropods.

The North American horseshoe crab is Limulus polyphemus of the family Limulidae.