Atlantic horseshoe crab

The Atlantic horseshoe crab (Limulus polyphemus), also known as the American horseshoe crab, is a species of marine and brackish cheliceratearthropod.[1] Despite their name, horseshoe crabs are more closely related to spiders, ticks, and scorpions than to crabs.[2] This species is found in the Gulf of Mexico and along the Atlantic coast of North America.[1] A main area of annual migration is Delaware Bay.[3]

Their eggs were eaten by Native Americans,[4] but today Atlantic horseshoe crabs are caught for use as fishing bait, in biomedicine (especially for Limulus amebocyte lysate) and science.[1] They play a major role in the local ecosystems, with their eggs providing an important food source for shorebirds, and the juveniles and adults being eaten by sea turtles.[1][3]

The other three extant (living) species in the family Limulidae are also called horseshoe crabs, but they are restricted to Asia.[5]