Horseshoe crabs are a common sight on beaches. Many people have seen some but do not realize they are looking at one of the oldest animals on the planet. Their ancestors can be traced back to around 445 million years ago, 200 million years before dinosaurs existed.
Horseshoe crabs are actually not true crabs at all, being more closely related to arachnids (a group that includes spiders and scorpions) than to crustaceans (a group that includes true crabs, lobsters, and shrimp).
Four species of horseshoe crabs exist today. Only one species, Limulus polyphemus, is found in North America along the Atlantic and Gulf coasts from Maine to Mexico. The other three species are found in Southeast Asia.
Their distinctive blue blood is used to detect dangerous Gram-negative bacteria such as E. coli in injectable drugs such as insulin, implantable medical devices such as knee replacements, and hospital instruments such as scalpels and IVs.
Components of this crab blood have a unique and invaluable talent for finding infection driving up an insatiable demand. A gallon alone costs $60,000.
Annually, the medical testing industry catches more than half a million horseshoe crabs to sample their blood. This overharvesting has led to a significant decline in crab populations. To address this, the harvesters take 30% of the blood from each crab, after which they are returned to the ocean.
But no one really knows what happens to the crabs once they're slipped back into the sea. In fact, among the females that do recover often breed less after being bled. Scientists believe that the biomedical industry's bleeding of these crabs may be endangering a creature that's been around since dinosaur days.
Experts are now looking for a synthetic alternative to lessen the adverse impact of the dwindling horseshoe crab population. If they do not find a better alternative, humans and commonly used animals in labs, are at risk.