The International Union for Conservation of Nature (IUCN) has recently started observing International Horseshoe Crab Day on 20th June. The intention of the day is to enhance awareness about preserving these ancient marine chelicerate arthropods.
About Horseshoe Crabs
Horseshoe crabs live in shallow coastal waters, generally on soft sandy or muddy bottoms, and spawn mostly on intertidal beaches at summer spring high tides. They come under the Subphylum Chelicerata, a division within Phylum Arthropoda, which also houses species like spiders, scorpions, mites, and ticks.
Arthropods are characterized by their segmented bodies and limbs and a thick chitinous cuticle, known as an exoskeleton. While most Chelicerata are found in terrestrial environments, horseshoe crabs are predominantly marine creatures.
Species and Habitats
Horseshoe crabs, often referred to as marine ‘living fossils,’ exist in four distinct species: the American horseshoe crab (Limulus polyphemus) inhabits the eastern coast of the USA and the Gulf of Mexico. The tri-spine, coastal, and mangrove horseshoe crabs (Tachypleus tridentatus, Tachypleus gigas, Carcinoscorpius rotundicauda respectively) are Indo-pacific species found in the coastal waters of India, Southeast Asia, China, and Japan, with their largest habitat in India being Odisha.
The Importance of Horseshoe Crabs
Since the age of dinosaurs, horseshoe crabs have served as crucial ecosystem engineers and predators of smaller organisms. They lay millions of eggs on beaches, becoming a feeding source for shorebirds, fish, and other wildlife. Their large hard shells provide a microhabitat for species such as sponges, mud crabs, mussels, and snails. Moreover, they act as a vital link to world health, biodiversity, and contribute cultural significance across the globe.
Threats Faced by Horseshoe Crabs
Horseshoe crabs face threats from overharvesting for food, bait, biomedical testing, and illicit trade for their supposed life-prolonging meat and aphrodisiac qualities. Their habitats are threatened by coastal reclamation, development, shoreline alterations designed to safeguard beaches from erosion and climate change-induced sea-level rise. These changes impact their spawning habitats. Poaching is also a rampant issue in many Indian states, contributing to their endangerment.
Conservation Efforts
The Wildlife Protection Act of 1972 has placed horseshoe crabs under Schedule IV, making it illegal to catch or kill them. Their IUCN status varies among species: the American horseshoe crab is listed as vulnerable, the tri-spine horseshoe crab as endangered, while the other two species have not yet been classified.
Inter-state coordination among police and wildlife authorities of Odisha, Bihar, Jharkhand, and other states is required to crackdown on horseshoe crab poaching. The Zoological Survey of India has proposed the declaration of horseshoe crab habitats as Eco-Sensitive Zones to enable better conservation and management of these unique creatures.
