Horseshoe crab

The horseshoe crab, horsefoot, king crab, or sauce-pan (Limulus polyphemus, formerly known as Limulus cyclops, Xiphosura americana, Polyphemus occidentalis) is a chelicerate arthropod. As a result, it is more closely related to spiders, ticks, and scorpions than to true crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America. A main area of annual migration is the Delaware Bay, although stray individuals occasionally turn up in Europe.

Three other species from the same family in the Indian and Pacific Oceans are also called horseshoe crabs. The Japanese horseshoe crab (Tachypleus gigas) is found in the Seto Inland Sea, and is considered an endangered species because of loss of habitat. Two other species occur along the east coast of India: Tachypleus tridentatus and Carcinoscorpius rotundicauda. A research project to protect them is on in Chandipur.