Horseshoe Crabs' Blood Is Used to Detect Infections. Now They’re Facing Extinction.
The demand for their blood is so high that it reportedly costs about $60,000 a gallon.
Horseshoe crabs have been on this planet for more than 450 million years — before dinosaurs and well before humans. But the existence of this arthropod is now under threat from continued human exploitation, according to Bloomberg.
Scientists discovered in the 1960s that horseshoe crabs' blood can be used as a clotting agent to detect the presence of bacteria. Before the finding, scientists had no easy way of testing whether vaccines, injections, and surgical implants had been contaminated by common bacteria like E. coli or salmonella. But the distinctive characteristic of the crabs’ blood made it simpler to detect even the smallest amounts of harmful bacteria.
About 30% of each crab’s blood is drained to make the medical supply and about 15% of the creatures do not survive the process. Those that live are re-introduced into the water, but their survival is difficult to track.
Since the medical use of horseshoe crabs’ blood was approved in the 1970s, pharmaceutical companies have caught 500,000 crabs along the US East Coast every year. The demand for their blood is so high that a gallon now reportedly costs about $60,000.
In 2016, the International Union for the Conservation of Nature included the American horseshoe crab on its “Red List of Threatened Species,” just one grade below being endangered. With overfishing and the climate crisis causing sea levels to rise resulting in habitat loss, some scientists estimate that 80% of the population has already been lost.
The crabs, also called “living fossils,” are important to the food chain and their decreasing numbers could also lead to the death of the shore birds, called red knots, that feed on them.
“Nobody has ever argued that the crab was going extinct. What we’re talking about is the collapse of an ecosystem, because a key species has been reduced," Larry Niles, a biologist for several nonprofit conservation groups, told Scientific American regarding the declining population of horseshoe crabs in New York State and New England.
The horseshoe crab population in the US mainly lives in the Atlantic Ocean, but can also be found in the waters of the US East Coast and Mexico’s Gulf Coast. Three other species of horseshoe crabs are known to live in the Indian Ocean and the Pacific Ocean along the coast of Asia.
According to Scientific American, population studies of these Asian species are also underway.
“I wouldn’t be surprised if they weren’t on the Red List very soon. The [Asian] populations are significantly declining,” John Dubczak, director of operations at Charles River Laboratories, a facility that makes Limulus amebocyte lysate — the extract from horseshoe crab blood — in South Carolina, told Scientific America.
Dubczak said his employees only harvest crabs by hand and that his operations do not pay for injured crabs, ensuring that the suppliers handle crabs with care.
“It reduces the injury, it reduces the stress, it’s better for [sustaining] the population, and it’s better for us,” he said, also noting that the mortality rate for crabs used by Charles River Laborities is just 4%.
“Between pollution, loss of habitat and the animals being eaten in Asia, their populations are under a tremendous amount of stress.”