Horseshoe Crab Blood May Save Your Life
Without help from horseshoe crab blood, we could die. So can shorebirds called red knots. And your dog. Seriously? And now with Covid-19, a vaccine may depend on horseshoe crab blood.

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

Horseshoe crabs have been around for 450 million years.

horseshoe crab blood

A fossil of a horseshoe crab

First, What Is A Horseshoe Crab?

But first, have you ever seen a horseshoe crab? Another misunderstood animal. They have been on our planet for about 450 million years, way before dinosaurs.

They are close cousins of the spider and look like big scorpions with hard-backed shells and long tails, With 10 legs and 10 eyes, they may look scary but are harmless.

Horseshoe Crab Blood

horseshoe crab blood

A bottle of horseshoe crab blood

But did you know we rely on horseshoe 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. And now any Covid-19 vaccines will first have to be tested with horseshoe crab blood.

Shorebirds And Horseshoe Crabs

Ok, so how do the shorebirds connect? The red knot shorebird has one of the longest bird migrations on the planet, almost 20,000 miles roundtrip. In order to fly such a long-distance, they fuel up on horseshoe crab eggs before they begin their journey.


horseshoe crab blood

Shorebirds, especially red knots, rely on horseshoe crab eggs for food.

horseshoe crab blood

Thousands of horseshoe crabs are captured in order to get some of their blue blood

Horseshoe Crab Populations Are Declining

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.

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?

horseshoe crab blood

If you see a horseshoe crab upside down, please turn it over so it can live

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.


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