Four horseshoe crab species are currently known to inhabit different geographical areas around the world. One of them, the tri-spine horseshoe crab, which inhabits the coastal waters of Japan, China, India, and Southeast Asia, has been declared an endangered species by the International Union for Conservation of Nature. Another horseshoe crab species, the Atlantic horseshoe crab, inhabits American waters and is considered nearly threatened. A recent study concluded that the Atlantic horseshoe crab is vulnerable to local extinction with an elevated risk in the Gulf of Maine area.1
Various factors have contributed to the endangerment of horseshoe crabs, including:2,3
Bleeding of Atlantic horseshoe crabs for Limulus amebocyte lysate (LAL) reagent production – The LAL assay is widely used for endotoxin testing and has found applications in the pharmaceutical industry, medical device manufacturing, and scientific research. The process of horseshoe crab capture and bleeding has been associated with substantial morbidity and mortality, as approximately 15% of the crabs do not survive the procedure.
Bleeding of tri-spine horseshoe crabs to produce TAL reagent, which is manufactured in Asia and is also used for endotoxin testing.
Horseshoe crab use as a bait for eel, whelk, and conch by commercial fisheries
Effects of gradual climate changes on horseshoe crabs, similar to those experienced by other ecosystems.
Natural mortality of horseshoe crabs, which may be caused by predators, beach strandings, and disease.
Human consumption of horseshoe crabs’ eggs or meat in some parts of the world.
Preservation efforts can help save horseshoe crabs from extinction and can have important implications not only for their ecological niche but also for the pharmaceutical industry, medical research, and environmental safety. Due to the complex causes of horseshoe crab endangerment, a multi-faceted approach is required to ensure their preservation.
Regulatory initiatives have been introduced to implement quotas for the annual harvesting of horseshoe crabs both for bait in fisheries and for bleeding for LAL reagent production.
Responsible practices for harvesting and bleeding – Simple steps can help reduce the morbidity and mortality associated with horseshoe crab bleeding. They include keeping horseshoe crabs in cool and moist environment, bleeding only healthy crabs, avoiding rebleeding by separating bled and unbled crabs, and returning bled crabs to ocean waters within 24 hours.
The development of recombinant endotoxin tests can help reduce and eventually eliminate the need for horseshoe crab bleeding. Recombinant endotoxin tests include recombinant Factor C reagents (rFC) and recombinant cascade reagents (rCR). FUJIFILM Wako has developed Pyrostar™ Neo – a recombinant cascade reagent that is a sensitive and specific synthetic alternative of the LAL assay.
The Just flip ‘em! Program – As hundreds of thousands of horseshoe crabs get stranded upside down on the beach and die each year, the Ecological Research & Development Group (ERDG) has launched the Just flip ‘em! Program. It encourages people, when they see a stranded horseshoe crab, to flip it over by holding it by the edge of its shell.