Horseshoe Crab Small

Horseshoe crabs represent a living fossil, having remained virtually unchanged for over 300 million years—predating dinosaurs by millions of years. Despite their crab-like appearance, they are more closely related to scorpions and spiders, belonging to the class Merostomata. These remarkable creatures feature a distinctive dome-shaped carapace and ten specialized legs adapted for navigating sandy and muddy seafloors. Their hard exoskeleton provides protection in marine environments, while their unique physiology—including blue copper-based blood—makes them invaluable to medical research and vaccine development. Horseshoe crabs play a critical ecological role as both predators of small invertebrates and prey for shorebirds, contributing to the health of coastal ecosystems. Their presence in an aquarium setup offers both educational value and a window into ancient marine biology.