Horseshoe Crabs: “Living Fossils” Imperiled in the Anthropocene

Abstract

The four species of horseshoe crabs are true “living fossils” with an evolutionary history that pre-dates the dinosaurs. One species, Limulus polyphemus, is found along the Atlantic and Gulf of Mexico coasts of North America. Three other species, the tri-spine horseshoe crab, Tachypleus tridentatus; coastal horseshoe crab, Tachypleus gigas; and mangrove horseshoe crab, Carcinoscorpius rotundicauda, live in shallow-water coastal and estuarine environments in Asia from Japan to India. Horseshoe crabs are valuable for human health because their blood is used to test for the presence of bacterial contamination in vaccines and other biomedical products. Today, all four horseshoe crab species are imperiled by overharvesting, shoreline development, and the loss and degradation of their essential spawning and nursery habitats. Despite these challenges, we remain optimistic that efforts to enhance conservation, including increased fishery management practices, marine protected areas, scientific research, public awareness, and citizen science engagement may together curtail further damage to their populations and enable recovery of these irreplaceable animals.