Horseshoe crabs’ ancestors appeared over 450 million years ago, making them are one of the very oldest species on Earth. They’re not actually crabs at all--they predate true crabs by at least a hundred million years, and are more closely related to spiders and scorpions. The four extant species of horseshoe crabs probably diverged between fifty and twenty million years ago. We don’t know for sure how they’ve lasted so long, but, in addition to their special blood, their ability to tolerate a wide range of environmental conditions has probably helped them survive. Learn more about their anatomy here, and our impact on them here and here. 

Until Fred bang discovered LAL in 1956, the only test we had for bacterial endotoxin contamination was injecting thousands of rabbits. In spite of it’s negative impacts, the LAL test is a huge improvement over this method. You can learn more about Bang’s discovery here. Learn more about the Gram Stain, the most common test for bacteria contamination, here.

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