The horseshoe crab is considered one of the relatively few living fossils on Earth, given that it's been around for 450 million years. But this prehistoric-looking, helmet-shaped invertebrate of the sea is a prized medical marvel - so much so that their blood is priced at $60,000 a gallon.
The horseshoe crab blood is so precious not because of its exotic blue color. Rather, the blood is prized for amebocytes - cells that move like amoebas to surround any invading pathogens. More than just isolating the pathogen, the amebocytes produce a gel-like seal that squelches the pathogen. This natural defense mechanism has allowed the horseshoe crab to survive in shallow, muddy waters, unchanged for hundreds of millions of years.
And lucky for us, the same mechanism also works to protect human blood against harmful pathogens. According to a report, the crab's blood can unmask endotoxins from gram-negative bacteria that would otherwise go undetected. Furthermore, the amebocyte's sensitivity is unparalleled, so much so that the FDA requires intravenous drugs, needles, and surgical equipment to first pass through the crab's blood.
The blue liquid is harvested during every spring mating season, when over 600,000 crabs are captured for blood donation. About 30 percent of the animal's blood is collected. The animal is then released. However, between 10-30 percent of the animals die in the process, exacerbating the already declining numbers.
Researchers are working to create a synthetic substitute that's as effective as the horseshoe crab blood. But until that version is available, we still have to rely on these ancient creatures to save countless lives.