(WHTM) June 8th is World Ocean Day, a day to contemplate the importance of the seas around us, and the creatures in them, to our very existence.
The Covid epidemic highlights this dependence. The success of the whole vaccination effort hinges on one particular creature-the horseshoe crab. There are four horseshoe crab species across the globe. If you’ve been to the beach, you may have encountered our local species, Limulus polyphemus-the Atlantic Horseshoe Crab.
(Horseshoe crabs aren’t really crabs at all. They’re more closely related to spiders, ticks and scorpions.)
Some people think horseshoe crabs are scary looking, or just ugly. They’re definitely in the “so ugly they’re cute” category. But horseshoe crabs are quite harmless. About the only one that could hurt you would be if you contrived a way to stab yourself with its tail. (The tail is actually called a telson. The crab uses it to steer, and to right itself if a wave flips it over)
Your chances of seeing horseshoe crabs are particularly good from May into July, especially if you visit the beach at the new or full moons. That is when high tides are at their highest, and that is when horseshoe crabs come ashore to breed.
The females crawl up the beach, dig down, and lay their eggs in the sand. A male will often hitch a ride on the female, holding her shell by his foremost legs. Sometimes another male will hitch a ride on the male in front of him, and another after that, until you have an amusing choochoo train crawling up the beach.
They’ve been doing this for four hundred million years.
No doubt about it, horseshoe crabs are survivors. Not only did they survive the asteroid that killed off the dinosaurs, they also made it through the Permian extinction 225 million years ago, when around 90% of all life on earth died out.
The question is, will they survive us?
Over the centuries they have been eaten, used as bait, and ground up as fertilizer. But right now, the biggest danger facing horseshoe crabs may be their own blood. It’s copper-based and turns blue when exposed to oxygen. (That’s right, they’re genuine bluebloods.)
The blood reacts strongly to bacterial infections; Limulus amebocyte lysate, or LAL, a chemical derived from the blood, is used to test for bacterial contamination of medical equipment-like that syringe that gave you your covid shot. At some point, a horseshoe crab may have saved your life.
But the only way to get this chemical is to siphon blood from horseshoe crabs. The worry is we’re taking too much blood from them. On average, the process takes 20-30 percent of a crab’s blood. (A human being has about 10 pints of blood; a 20-30 percent draw would be 2-3 pints.)
Scientists tag crabs to track their comings and goings and conduct annual crab counts up and down the east coast.
Right now the International Union for Conservation of Nature lists the Atlantic horseshoe crab as “vulnerable”, just one step below endangered.
This put us and the crabs in a difficult situation. We’re going to need more and more LAL, and if there are fewer and fewer crabs, we could trigger the extinction of all four horseshoe crab species on the planet.
But there is hope on the horizon. An artificial substitute for LAL, Recombinant factor C (rFC) is gaining acceptance.
In the meantime, we can help horseshoe crabs in our own small way. If you find one on the beach that’s been flipped upside down by waves, turn it right side up so it can go on its way. For creatures that have been saving our lives for decades, it’s the least we can do.