Horseshoe Crabs And Why We’re All Vampires

Image Source: Public Domain

Enter the horseshoe crab. At 450 million years old, the beautiful animal is considered a living fossil. It’s outlived the dinosaurs, surviving not just their extinction but severe changes to the Earth’s climate. Ice ages and asteroids couldn’t kill them off. But today they have a unique predator: humans. And it’s not their meat that we want. No. We want their blood.
1

Human’s drain horseshoe crabs of their blood, which is blue and eerily reminiscent of a sci-fi film. And this azure liquid is absolutely vital to the foundation of the world’s medical system, and therefore, modern society. You see, horseshoe crabs have a special way of responding to bacterial infection. Our blood is red due to the hemoglobin and iron used to carry oxygen molecules for use in ATP production. Horseshoe crabs use copper and hemocyanin, which makes it blue. This blue blood contains a special protein called coagulin. What coagulin does is form a kind of gel-like substance to stop invading bacteria in their tracks. From there, the organism’s amebocytes can easily take them out.

2
3
4

This jelly substance is very helpful at detecting bacteria, particularly, their endotoxins. Endotoxins are part of a gram-negative bacteria’s outer membrane. Composed of lipopolysaccharides (fats and sugars, LPS). LPS helps the bacteria’s cell wall maintain structural integrity. It’s a vital building block of keeping the bacteria cell together. This endotoxin is what’s called an antigen, basically a calling card or signal for our body to know that something is a ‘foreign contaminant’. When our body detects the ‘antigen’, our immune system kicks into gear. One consequence of this immune response is fever and ‘feeling sick’. This is something most people don’t know, that the feeling of sick isn’t necessarily the bacteria or whatever. Our body makes itself sick as part of the process of recovery.
5
6

The coagulin of horseshoe crabs detects the presence of endotoxins. We use it to ensure that any medicine or instrument is clean of endotoxins. This ranges from anything to insulin to an IV needle to a surgical implant to a vaccine shot. Really, the entire medical system and pharmaceutical industry relies on this method to ensure quality control. Without it, we’d be at risk of causing infection every time we tried to give somebody a shot! If the poison is high enough and enter’s a person’s spinal fluid or blood stream, they can get septic shock, organ failure and death.

7
8

This is why we’re vampires. We go out to the coasts of Eastern United States when the horseshoe crabs are mating on a full moon. They cover each other, sometimes ten males trying to mate with a single female, some with broken shells that would have killed other organisms lacking that special blue-blooded bacterial resistance. And we take upwards of 500,000 crabs, carefully by hand, to special cleaning facilities. We clean them off of sand, dirt and barnacles, and then put them in super-clean blood draining rooms. The goal is about 1/3 of the organism’s blood. About 15% won’t survive the procedure. All this has to happen in about 24 hours. From there, we put them back in the sea on special little water-slides. This process is heavily regulated, but it still poses a major problem.

9

There are two types of crabs we use for bloodletting, TAL and LAL. TAL stands for Tachypleus Amoebocyte Lysate, and exists in Asia. LAL stands for Limulus Amoebocyte Lysate and is in the United States. LAL blood letting is regulated, whereas TAL isn’t. And the farming process for TAL means the death of a LOT of crabs. So much so, that their population is now considered endangered. The problem of LAL farming is that migratory birds including Red Knot, which travels from South America to the Arctic Circle of Canada, rely on the eggs of horseshoe crabs. Their population is now dwindling because of their favorite food on their rest stop is missing.
10

There is currently a push to use a synthetically produced protein, recombinant factor C (rFC) in place of horse shoe crab blood. Doing so would reduce the reliance on their blood, possibly preventing them from endangerment by medical blood letting. Of course, their vulnerability to human society, as with all animal life, remains.

Sources

1
2
3
4
5
6
7
8
9
10