Bad Blood

A brewing lawsuit considers the fate of an ancient species

Scientists bleed horseshoe crabs to extract blue, copper-based blood. JEFF ROTMAN / ALAMY PHOTO
31 July, 2022

In the wake of a global health crisis, it is worth taking a moment to appreciate the humble horseshoe crab. According to the South Carolina Department of Natural Resources, “if you have ever needed a vaccine … you most likely benefited from the use of horseshoe crab blood.” The SCDNR would know—it is facing a lawsuit on the subject. 

Horseshoe crabs are a common sight in South Carolina, a rural state on the south-eastern coast of the United States covering roughly the same area as Jharkhand but with a population smaller than Himachal Pradesh. The state’s coastline is a picturesque labyrinth of interweaving barrier islands, saltwater marshes and sandy beaches. Every spring, Atlantic horseshoe crabs converge here by the tens of thousands to spawn, just as they have since time immemorial.

“Time immemorial” is no hyperbole. Horseshoe crabs are an ancient species. So much so that calling them Atlantic horseshoe crabs seems parochial—they existed long before there was such a thing as the Atlantic Ocean. The oldest known horseshoe crab species lived almost half a billion years ago, predating the first dinosaurs, the first flowers, and all modern oceans and continents.

The common-sounding name fails to reflect not only their remarkable persistence as a species but also their extraordinary physical appearance. They resemble horseshoes only in the way that anything semi-circular does, and they are more closely related to spiders than crabs. A more accurate description would be “hard-shell stingray”—or even “organic Roomba.” Truthfully, they call to mind the face-hugger creatures from Ridley Scott’s Alien more than anything else. (“Alien” is an unavoidable word upon first sight of a horseshoe crab. They have ten eyes, ten legs and a stiff tail as long as the rest of their body.)