Horseshoe Crabs May Have Saved Your Life

Submitted by Deborah Cramer

Horseshoe Crabs May Have Saved Your Life
Spawning horseshoe crabs, Moore’s Beach, Delaware Bay, New Jersey
© Steve Greer

Perhaps, walking the wrack line along a gentle sandy beach in the summer, you’ve seen the empty molts of horseshoe crabs. Perhaps, if you are lucky, you’ve seen a beach cobbled with horseshoe crabs spawning during the spring high tides. These ancientlooking animals, more closely related to spiders than crabs, have lived in the sea for 445 million years, surviving five major mass extinctions. Horseshoe crabs can’t walk backward and retrace their steps, but their unique way of fighting infection has proved indispensable to our well-being.

If you’ve ever received a flu shot or medication from an IV line, or if you have a pacemaker or another surgically implanted medical device, chances are that a horseshoe crab has saved you from a life-threatening infection. The blood of horseshoe crabs, colored blue by the presence of copper, clots in the presence of toxic bacteria.

Pharmaceutical companies test the purity of IV drugs, vaccines, medical devices, and the water used to produce them, with Limulus amebocyte lysate (LAL). LAL is made from horseshoe crab blood cells separated from the plasma, then broken, or lysed, to release the toxin detector.

LAL is unique: researchers have yet to synthesize its equivalent, making the blue blood of horseshoe crabs the gold standard for quality control in pharmaceuticals.

Each year, some 360,000 horseshoe crabs donate their blood for the production of LAL. Some die in the process. Increased understanding of how much blood a horseshoe crab actually has, how much can be safely extracted, and how to reduce the animals’ stress during their 72 hours out of the water, can help sustain the population of crabs.

Horseshoe Crabs May Have Saved Your Life
Horseshoe crabs in Mispillion Harbor, Delaware Bay
© Barrie Britton

p.s. LAL is not the horseshoe crab’s only contribution to human well-being. Scientist H. K. Hartline, studying the large eyes of horseshoe crabs, uncovered the relationship between light reception and animal vision. His work won a Nobel Prize.

p.p.s. Humans are not the only animals to depend on horseshoe crabs. Migrating birds do as well. Red knots depend on a diet rich in horseshoe crab eggs to sustain them on the last leg of their annual journey from Tierra del Fuego to their nesting grounds in the Arctic.

References and more information

Novitsky, Thomas J. 2009. Biomedical Applications of Limulus Amebocyte Lysate. In The Biology and Conservation of Horseshoe Crabs, John.T. Tanacredi, Mark L. Botton and David R. Smith, eds. 315-329. New York: Springer.

Hurton, L., J. Berson, and S. Smith. 2009. The Effect of Hemolymph Extraction Volume and Handling Stress on Horseshoe Crab Mortality. In The Biology and Conservation of Horseshoe Crabs, John.T. Tanacredi, Mark L. Botton and David R. Smith, eds. 331-346. New York: Springer.

Robert B. Barlow. 2009. Vision in Horseshoe Crabs. In The Biology and Conservation of Horseshoe Crabs, John.T. Tanacredi, Mark L. Botton and David R. Smith, eds. 223-235. New York: Springer.

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