If you've ever had a flu shot, know someone with a pace maker or joint replacement, or have given your pet a rabies vaccination, you owe a debt of gratitude to the horseshoe crab. Vaccines, injectable drugs, intravenous solutions, and implantable medical devices, both for humans and animals, are quality checked for safety using a test that comes from the blood of horseshoe crabs. Most recently, horseshoe crabs have been in the news due to the coronavirus pandemic, and the need for testing of vaccines, once available. This is a really big problem for our struggling horseshoe crab populations.
Every year, over 500,000 horseshoe crabs are captured and “bled” in laboratories for their blue blood. Commercial fishermen, contracted by biomedical companies withdrawing the blood, capture the crabs during their spring spawning season, then transport them to labs where up to 30% of their blood is removed from their bodies. The crabs are then released far from the site of capture, to ensure they are not bled a second time.
Why would anyone do such a thing to this ancient, harmless creature? If you’re alive, you’ve probably benefitted from this practice more than once. The blue blood of horseshoe crabs, is used to detect harmful bacteria in vaccinations, prosthetics and other medical devices like pacemakers.
To manufacture Limulus amebocyte lysate, commonly referred to as LAL, biotech companies collect adult horseshoe crabs, remove their blood, then release them alive. Approximately 15 percent of the animals do not survive the bleeding procedure. As of 2016 the bleeding mortality associated with LAL production was estimated to be 70,600 animals per year.
In addition to the use of their blood for an endotoxin test such as the gel clot test, the horseshoe crab's DNA has been used to develop a recombinant test method for endotoxin.
Even as alternatives are being developed that will retire or reduce the use of horseshoe crab blood, we will always be indebted to the horseshoe crab's contribution to our overall health.
Horseshoe Crab Identification
Horseshoe crab identification is pretty straightforward since there aren't many animals you can confuse them with. Browse the slides below to learn how to tell the difference between male and female Atlantic horseshoe crabs, how to identify their many legs and eyes, then download Horseshoe SOS to learn even more about them as well as the other three species occurring in different parts of the world. Be sure to check out the ERDG profile page in the app for opportunities to get involved in horseshoe crab conservation. You can become a valuable citizen scientist by reporting tagged horseshoe crabs (dead or alive), or detached tags you find on the beach, to the US Fish and Wildlife Service using the Report button in the app.