Horseshoe crabs might look like a prehistoric relic from a bygone age, but this 450-million-year-old species plays a surprisingly important role in modern medicine and could soon find themselves as a key player in the development of a Covid-19 vaccine.
Unlike the iron-rich blood in us and other mammals, Atlantic horseshoe crabs (Limulus polyphemus) have copper-rich blood that’s icy blue in color. Instead of white blood cells, their blood is filled with cells known as amebocytes, which are extremely effective at detecting bacterial endotoxins. Even at levels less than one part per trillion, amebocytes trigger the formation of coagulation, turning the blood into a jelly substance.
This trait has been exploited by food producers and pharmaceutical companies for decades to test whether their products, such as their vaccines, are free from bacterial contamination. Wild populations of Atlantic horseshoe crabs have long been under pressure thanks to their lucrative blood, leading conservationists to push pharmaceutical companies to opt for human-made alternatives.
The debate has recently been given more fuel due to anticipated demand for crab blood in the development of Covid-19 vaccines, according to The New York Times. After all, rolling out a Covid-19 vaccine would mean millions, if not billions, of vaccines to undergo endotoxin testing.
Horseshoe Crab Recovery Coalition (HCRC) – which includes the National Wildlife Federation, Defenders of Wildlife, and many other conservation organizations – has recently called on pharmaceutical companies to switch to a synthetic equivalent called recombinant Factor C (rFC).
“It is unfortunate that biomedical research still relies on the harvesting of a vulnerable wild animal population when there is a simple, effective, sustainable replacement that could exist in plentiful supply,” Ryan Phelan, co-founder and executive director of Revive & Restore, said in a statement.
While the impact of blood harvest on the wild Atlantic horseshoe crab populations is disputed, the IUCN Red List states the species is currently vulnerable to extinction and continuing to decline. The species can be found off much of the Atlantic coast of America, from the Mexican coastal regions of Yucatán Quintana Roo to the US coast as far north as Maine and New Hampshire.
Despite their name, they are not actually crabs or even crustaceans but belong to a group known as Xiphosura that has scarcely changed in hundreds of millions of years. The earliest fossil horseshoe crabs are roughly 450 million years old, meaning these unusual creatures were around 200 million years before the dinosaurs.
They’ve managed to survive a handful of extinction events, but could humans be their downfall? It’s uncertain for now, but the few years ahead will certainly turn up the heat on this vulnerable species.