Horseshoe crabs are true blue bloods. For over 40 years, scientists have used their fluorescent blue blood to test vaccine safety and when the COVID-19 vaccine candidates are finally tested, the horseshoe crab will play a vital role. Their blood is harvested to make the Limulus amebocyte test, or LAL test, that is the gold standard to detect toxins in vaccines and other injectable drugs.

According to USA Today, the Atlantic horseshoe crab lives only on the eastern coast of North America and in certain areas in Central America. Approximately a half million of these crustaceans were brought to biomedical facilities in 2018, according to the latest figures by Atlantic States Marine Fisheries Commission.

When the crabs arrive at a facility, they undergo a bleeding process that removes 30% of their blood, according to USA Today. Not all survive the process, and the mortality rate is between 3% to 15%. Before the LAL test was developed, scientists injected rabbits with potential vaccines to test their safety. If the rabbit became ill or died, the vaccine or drug was considered unsafe.

The Baltimore Sun reported that a synthetic crab blood substitute that detects toxins in injectable or implanted medical products is available, but the cost is about the same as fresh blood. Therefore, pharmaceutical companies like Eli Lilly are not motivated to switch, despite the fact such a move would be environmentally friendly and help sustain the horseshoe crab.

No matter which vaccine wins the race to fight COVID-19, LAL from the blood of horseshoe crabs will be employed to test the safety of all the components of the medication as well as the vaccine itself, according USA today.

“The world’s healthcare can thank the horseshoe crab,” said Allen Burgenson, chairman of the Horseshoe Crabs Advisory Panel to the Atlantic States Marine Fisheries Commission, according to USA Today.