Horseshoe Crabs

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    • Scientists have urged the Odisha government to immediately come up with a robust protection mechanism before the horseshoe crabs become extinct due to destructive fishing practices. 

    About Horseshoe Crab

    • Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and the only living members of the order Xiphosura.
    • Four living species of horseshoe crabs:
      • Limulus polyphemus, the Atlantic or American horseshoe crab, found along the Atlantic coast of the United States and the Southeast Gulf of Mexico.
      • The tri-spine horseshoe crab (Tachypleus tridentatus), the coastal horseshoe crab (Tachypleus gigas) and the mangrove horseshoe crab (Carcinoscorpius rotundicauda) in coastal waters of India, southeast Asia, China and Japan. 
    • They have been around for more than 300 million years, making them even older than dinosaurs. They look like prehistoric crabs, but are actually more closely related to scorpions and spiders. 
    • The horseshoe crab has a hard exoskeleton and 10 legs, which it uses for walking along the seafloor.
    • Female horseshoe crabs are about one-third larger than the males. 

    Habitat:

    • Horseshoe crabs utilize different habitats depending on their stage of development.
    • The eggs are laid on coastal beaches in late spring and summer. After hatching, the juvenile horseshoe crabs can be found offshore on the sandy ocean floor of tidal flats. Adult horseshoe crabs feed deeper in the ocean until they return to the beach to spawn.
    • Maximum density of Horseshoe crabs is found along the Odisha coast and Balasore used to be the largest spawning ground. 

    Threats:

    • Day by day, the population of the blue blood crabs is decreasing. After 10 years, there will not be any Horseshoe crab in India.
    • Overharvesting for use as food, bait and biomedical testing, and because of habitat loss from coastal reclamation and development. 
    • Shoreline alterations that are engineered to protect beaches from erosion and sea level rise due to climate change also affect their spawning habitats.

    Medicinal Use 

    • A horseshoe crab’s bright blue blood is used to test vaccines, drugs and medical devices to ensure that they aren’t contaminated with dangerous bacterial toxins. 
    • A horseshoe crab’s blood contains a special clotting agent limulus amebocyte lysate (LAL) which detects a contaminant called endotoxin. If even tiny amounts of endotoxin make their way into vaccines or injectable drugs, the results can be deadly. 
    • Therefore, it has been essential for testing the safety of biomedical products since the 1970s, when it replaced rabbit testing. 
    • Every year, pharmaceutical companies roundup half a million Atlantic horseshoe crabs, bleed them, and return them to the ocean after which many will die. 

    Conservation Status:

    • The American horseshoe crab is listed as Vulnerable to extinction and the tri-spine horseshoe crab is classified as Endangered on the IUCN Red List of Threatened Species.
    • Horseshoe crabs are listed under Schedule IV of India’s Wildlife Protection Act, 1972.

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