Horseshoe Crab

The horseshoe crab is an ancient marine arthropod found along the Atlantic coast of North America and the coasts of Southeast Asia, with a lineage that fossil evidence suggests has changed little for hundreds of millions of years, earning it a reputation as a living fossil. Despite its name, it is not a true crab or crustacean but is more closely related to spiders and scorpions, identifiable by its hard, rounded, horseshoe-shaped shell, long pointed tail spine and multiple pairs of legs used for walking and feeding on worms, mollusks and other small invertebrates on the sea floor. Each spring, horseshoe crabs gather in enormous numbers on certain beaches to spawn, laying eggs that provide a critical food source for migratory shorebirds. Its distinctive blue, copper-based blood contains a compound used by the pharmaceutical industry to test injectable drugs and vaccines for bacterial contamination, leading to large-scale harvesting of wild horseshoe crabs. Habitat loss and overharvesting for bait and biomedical use have caused population declines in parts of its range.