Horseshoe crabs, also known as Limulidae, are ancient marine arthropods that have been around for over 300 million years, predating even the dinosaurs. These fascinating creatures are found along the Atlantic and Pacific coasts of North America and Asia, inhabiting shallow, sandy or muddy bottoms. Horseshoe crabs are characterized by their distinctive horseshoe-shaped shell, which protects their delicate bodies. They have ten legs, of which the first pair is modified into chelicerae for grasping prey. Horseshoe crabs are filter feeders, using their specialized legs to sift through sand and mud for small worms, crustaceans, and mollusks. These ancient arthropods play a crucial role in the marine ecosystem. They serve as food for various marine predators, including fish, birds, and shorebirds. Their eggs, which are laid in large numbers along shorelines, are a vital food source for migratory birds. Additionally, horseshoe crabs' blood contains a unique compound called amebocyte lysate (AL), which is used in the manufacturing of medical diagnostics. Despite their ecological and economic importance, horseshoe crabs face numerous threats, including habitat loss, overfishing, and biomedical bleeding. Conservation efforts are underway to protect these vital creatures and ensure their continued survival in the marine environment.