Horseshoe crabs have been around about 450 million years longer than horseshoes. So it’s sort of a strange name for these breathing fossils, but they do kind of have the shape of a horseshoe I guess, when you think about it. Appearing during the Ordovician period (a time dominated by marine life) the horseshoe crab emerged just in time for a series of mass extinctions of life on earth; caused by millions of meteors bombarding the globe’s surface. Not that the horseshoe crabs had anything to do with this but in true survivor mode they soldiered on as 60 % of all other life in the ocean perished.
Fast forward to today when once again they are threatened, this time by humans who can often be much more destructive than meteors. We are messing with the muddy and sandy shorelines they require, in order to reproduce, and this not only affects them but also the migratory birds who will often feed on their eggs.
Let’s rewind to the beginning; the hard shell of the horseshoe crab is their protection (good for dodging Meteors, well smaller ones anyway) against a wide array of predators both in the ocean and on land. They are Arthropods, meaning they have a segmented exoskeleton or shell. This shell (or carapace) is the same kind that spiders, scorpions and lobsters (who are also Arthropod associates) have for protection. But even though they resemble crabs, and other crustaceans they are more closely related to arachnids (spiders). They will shed this shell several times as they grow to be about 16 inches in length.
Throughout the 450 million year run of the Horseshoe Crab they have remained remarkably unchanged. Oh a tweak here and there but if it ain’t broke, why fix it? However this doesn’t mean that they’re not exceedingly weird creatures. Their shell resembles the helmets the rebels wear in “Star Wars”, and when you turn them over they look like the creature stuck to John Hurt’s face in “Alien”. I guess if you think about it, their ancient origins make them the perfect other worldly looking creature, to utilize in outer space settings.
And we are not done yet with the list of extraordinarily bizarre things about them. Their legs (they have 10 and can regenerate them if need be) surround their mouth and are used for a wide array of functions including swimming (which they do upside down) crawling on land (which they do right side up) and feeding themselves whatever they can find (though they mostly like clams and worms). Their legs also crush up their food before they eat it. Below the mouth they have gills which can also double as lungs for short periods of time on land. They possess multiple eyes but cannot see very well except at night. Finally, although they look menacing with the spikes in back and the rapier like tail, they're not. Their tail is used mostly to right themselves on land, if they happen to get turned over.
And most importantly the horseshoe crab is the royalty of the ocean, as their blood is naturally baby blue in color. It has blue blood because it uses hemocyanin (it contains copper which makes it blue) instead of hemoglobin (red) to carry the oxygen in their blood. Quite possibly their special blood has helped them survive all these millions of years.
A quart of this royal blood will set you back fifteen grand. Which is a lot for blood, but then regular blood does not clot around bacteria in the swift and complete manner that the horseshoe crab’s does. Making it ideal for finding contaminants during medical trials for new drugs. This of course (like anything having to do with medicine) drives the price up considerably. Not that the beleaguered horseshoe crab benefits at all from any of this. Quite the opposite but if they can survive meteors this too shall pass.