Originally Published September 2000
The plight of the horseshoe crab points up the fragile bond between increasingly threatened natural resources and medical innovation.
Nearly ten years ago to the day, I stared in puzzlement at the very first press release I would edit as a staff member on a medical device magazine. The document was for something called the limulus amebocyte lysate (LAL) diagnostic assay, and the notion of "not being able to make heads or tails" of the thing would have immediately suggested itself had I not suddenly come upon an illustration featuring the distinctly recognizable head and tail of a very old acquaintance. In fact, this companion of my childhood—more precisely, of several summers on the beach at the Jersey shore—has been around for some 400 million years, since before the dinosaurs. Its scientific name is Limulus polyphemus, with its echo of the fearsome Cyclops who tormented Ulysses. But despite its spiky carapace and rapier-like tail, the horseshoe crab, I remembered clearly, is one of the gentlest and most accommodating of creatures.
First of all, it's not a crab at all, but a relative of the spider, tick, and scorpion. Unlike these irritable cousins, however, the horseshoe crab is entirely inoffensive and actually rather hapless: that intimidating-looking tail, for instance, is used not to sting but as a sort of fulcrum to right itself if it happens to flip upside down. The male especially, I'm afraid to say, is both listless and brotherly in a queasy sort of way. During the communal late-Spring mating ritual centered along the Delaware Bay, the female digs a nest, deposits some 20,000 pearly green eggs, and then is obliged to drag one or several reluctant males, each holding onto his neighbor's tail, over the eggs to fertilize them. The eggs of the horseshoe crab are critical to millions of migrating birds flying north from their wintering habitats in Central and South America; the hungry birds have been known to double or triple their weight before moving on.
The crabs have also provided a surprising level of sustenance for medical researchers. In the 1950s, it was discovered that the blue-colored blood of the horseshoe crab contains special cells—the LAL that baffled me in the press release—that kill certain kinds of bacteria. This extract is now used by pharmaceutical and medical device manufacturers to test for the presence of endotoxins. The crabs have also proved useful for cancer research—for example, in the diagnosis of leukemia. A rare protein has been found in the crab's blood that traces and binds with vitamin B12, which has led to novel test kits for B12-related deficiencies and diseases, including pernicious anemia and various intestinal disorders. Experiments recording electrical impulses from the crab's optic nerve in its lateral eye resulted in the discovery of many of the principles underlying the functioning of all visual systems, and garnered a Nobel prize for the human participant.
Since the day in 1990 that I reacquainted myself with the beneficent peculiarities of the horseshoe crab, their numbers have fallen by 90%. The federal government is belatedly attempting to restrict the crab harvest, and is generally meeting with cooperation from all quarters with the exception of the benighted state of Virginia, which apparently objects to the 10% of crabs not yet converted into 100% catfish and eel bait.
As kids, we confused the idea of the lucky horseshoe with that of the lucky horseshoe crab, and doubly prized the molted shells collected from the surf. Despite its generous contributions to human well-being, it seems the crab's luck is running out faster than a rip tide.
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