You see them washed up on a Glynn County island beach, and they’re not exactly pretty. 

Horseshoe crabs look like weirdly configured helmets. They range in color from brown or brown-green to reddish, with spikes on their tail section. And unless you’re a bird or a fish, they’re nothing you would regard as good food.

But, ah. Horseshoe crabs are so important.

These animals are 450 million years old. They have survived four global extinctions. They are, truth be told, not crustaceans as are most crabs, but rather, arthropods, which means they’re more closely related to spiders. 

What makes them vital – for humans – is their milky-blue blood. It contains a substance known as limulus amebocyte lysate, which detects a type of harmful bacteria known as an endotoxin.

If an endotoxin creeps into vaccines, other drugs, or even into artificial hips and knees that are used as replacements, lives can be lost.

Horseshoe-crabs blood is the only known natural source for that pharmaceutical endotoxin, which costs $60,000 per gallon. That blood has saved countless lives since it was discovered in 1956 to be an infection remedy.

It is why, each spring, under a full moon, as the crabs crawl across Atlantic Coast beaches to lay their eggs, pharmaceutical companies collect a half-million horseshoe crabs. Blood is drawn, and the animals are returned to the sea. 

It seems like a win-win for everyone. But, sadly, it is not. Not for the horseshoe crab. Nor for migratory birds and fish that depend on the crab’s protein-rich eggs for survival.

Horseshoe crab populations have fallen sharply in some locations. It has not helped that horseshoe crabs are popular in some places as fish bait. And, so, the species has come under protection as scientists continue to work, with promise, on a manufactured option for horseshoe-crab blood.

A wondrous animal that has survived 450 million years and four global extinctions is battling again to stay alive. If its usual good fortunes prevail, horseshoe crabs will remain with us for a few more millennia, at least.

-Lynn Henning, author and journalist

**Picture by PBS**