Without help from horseshoe crab blood, we could all die.  So can shorebirds called red knots. And so could your dog. Seriously?

We are all connected. We hear that phrase so many times we tend to discount it. But how are humans, horseshoe crabs, dogs, and shorebirds all connected? This is starting to sound like a bad sci-fi movie.

horseshoe crab blood

A horseshoe crab shell at Folly Beach, SC

But first, have you ever seen a horseshoe crab? They have been on our planet for about 450 million years, long before the dinosaurs. They are close cousins of the spider and look like big scorpions with hard-backed shells and long scary tails, but are harmless.  We remember finding the empty shells of these cool looking crabs along the shore as kids.

Horseshoe Crab Blood

But what we never knew is people rely on the crabs to make sure our blood supply is free of bacteria. Really? When exposed to toxins, the crabs use their blood, which is blue from the copper in it, to isolate the toxin and enclose it with a gel.  This gel keeps them from getting sick. When the crab’s blue blood is exposed to human blood, it reveals any bacteria that might otherwise go undetected.

As a result, all intravenous drugs, including shots and vaccines, in the US are required by the FDA to be tested with horseshoe crab blood to detect any foreign bacteria. Wow! That includes your flu shot and your dog’s rabies shot (ahh, that’s how dogs tie-in!). Also, your medical implant (think knee or hip replacement) or contact lens has been checked for contamination using the horseshoe crab’s blood.

horseshoe crab blood

Red Knot Shorebird looking for horseshoe crab eggs.

Shorebirds and Horseshoe Crabs are Connected

Ok, so how do the shorebirds connect? The red knot shorebird relies on the consumption of eggs laid by the horseshoe crab to fuel their unbelievably long migration from South America to the Arctic (almost 20,000 miles round trip). They stop at Delaware Beach (the largest population of horseshoe crabs in the world) to gorge on crab eggs in order to survive the long flight.

So how is their blood harvested and does it hurt the horseshoe crab? The crabs are caught, transported to a lab and hooked up to a machine that pierces their shell and drains 30% of their blood. Yikes, we sound like vampires! The crabs are then returned to the ocean where some (estimates range from 10-30%) die or stop reproducing.

horseshoe crab blood

Horseshoe Crabs mating. Photo by Hayden via Wikimedia Commons, Creative Commons License

The crabs are also harvested as bait for fishing further reducing their populations. Horseshoe crabs are now classified as Vulnerable by the International Union for Conservation of Nature (IUCN), which means they are likely to become endangered if conditions do not improve.

How Can We Help?

They do so much for us, so what can we do for them?  To begin with, if you see one upside down and alive, gently turn it over so it can live. They get tumbled about in the waves and have no way of righting themselves if flipped. Second, you can learn all you can about these incredible creatures and truly appreciate all they do. Become an advocate for research to find alternative methods of testing for toxins. Or at a minimum, support groups that are finding ways to reduce the mortality rate and stress factors while harvesting their blood.

We owe our lives to horseshoe crabs. Let’s protect them because it is the right thing to do.

horseshoe crab blood

Upside down horseshoe crab. Please turn me over so I can live.



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