Horseshoe Crab (Limulus)

The horseshoe crab (Limulus polyphemus) is a chelicerate arthropod, therefore it is more closely related to spiders and scorpions than crabs. They 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.

A Japanese variant (Tachypleus tridentatus) is found in the Seto Inland Sea, but is considered an endangered species because of loss of habitat. They can grow up to 20 inches (51 cm), on a diet of mollusks, annelid worms, and other invertebrates. They find these prey under the sand, where they spend most of their lives. In captivity, its diet should be supplemented with meaty items such as pieces of squid and shrimp (Foster and Smith, 2004). Its mouth is located in the middle of the underside of the cephalothorax. A pair of pincers (chelicerae) for seizing food are found on each side of the mouth.