Horseshoe crabs are fascinating marine arthropods that have existed for over 450 million years, making them one of the oldest species still alive today. Despite their name, they are more closely related to spiders and scorpions than true crabs. Horseshoe crabs are easily recognized by their hard, horseshoe-shaped exoskeleton and long, spiked tail (telson), which helps them flip over if they end up on their backs.They are most commonly found along the coasts of North America and Southeast Asia, particularly in shallow waters and mudflats. Horseshoe crabs play a vital role in marine ecosystems, serving as food for birds and fish. Their blue blood, rich in a substance called Limulus Amebocyte Lysate (LAL), is also highly valued in medical science for detecting bacterial contamination in vaccines and medical equipment.Despite their ancient lineage, horseshoe crabs face increasing threats from habitat loss, overharvesting (for bait and medical purposes), and climate change. Conservation efforts are underway to protect this unique and ecologically important species.