Horseshoe Crab

 

The Atlantic horseshoe crab (Limulus polyphemus) is Maryland's oldest living fossil, having inhabited the region's shallow waters for roughly 350 to 450 million years—meaning they predated the dinosaurs and even the formation of the Chesapeake Bay itself. Despite their deceptive name, these armored invertebrates are not true crabs at all; they are ancient chelicerates more closely related to terrestrial spiders and scorpions. In Southern Maryland's history, Native Americans like the Roanoke Island tribes originally used their stiff, spike-like telson tails to tip fish spears, while early European settlers and 20th-century farmers harvested millions of them to grind into agricultural fertilizer and poultry feed. Today, horseshoe crabs are fiercely protected and deeply valued in Southern Maryland for two major reasons: The Ecological Buffet: Every spring and summer, particularly during the high tides of new and full moons in June, thousands of these gentle giants migrate onto sandy, protected Bay beaches to spawn. A single female can lay up to 20,000 tiny greenish eggs, creating a critical, nutrient-rich seasonal buffet that powers endangered migratory shorebirds—like the red knot—on their journey to the Arctic. The Blue Blood Miracle: For modern medicine, the horseshoe crab is a literal lifesaver. They possess copper-based, bright blue blood containing Limulus Amebocyte Lysate (LAL). LAL is an incredibly sensitive substance used globally to test the purity of vaccines, intravenous drugs, and medical devices for dangerous bacterial endotoxins. Specially permitted medical facilities carefully harvest a portion of their blood before releasing the live creatures safely back into the wild.