The Ancients Among Us
There are ancient creatures living among us, some hiding in plain sight and others we’ll likely never see. I recently became acquainted with one and re-acquainted with another vaguely recalled from childhood.
Both of these creatures have existed, mostly unchanged for hundreds of millions of years; both earn their living in the brine, one in the temperate waters of the Atlantic off the US east coast, the other in the dark, frigid depths of Pacific off the coast of Oregon.
The first is the primal looking Horseshoe Crab found in the Chesapeake and along the mid-Atlantic coast. These creatures are actually more closely related to spiders, ticks and scorpions than they are to crabs. With their helmet-like carapace and rigid pointy tail called a ‘tensor’, the Horseshoe Crab presents an imposing appearance. First appearing around 250 million years-ago (mya) and little changed since, Horseshoe Crabs are considered ‘living fossils’ by science.
I’d first encountered these guys while visiting Connecticut as a kid and had largely forgotten them. A few years back I was spending some time on the Eastern Shore of Maryland and was re-acquainted with the horseshoe crab. Despite having a LARGE compound eye on each side of their heads and seven simple eyes elsewhere, they have relatively poor vision.
Even so, I noticed this one crab coming toward me as if it recognized me. I could see its compound eye looking right at me and had to wonder what it saw. Something had the creature’s attention as it sat there with that one menacing compound eye on me. The shallow water revealed the horseshoe shape of the carapace that meets with a flounder-like hinged rear ending in the tensor.
Another bizarre aspect of the horseshoe crab’s physiology is its blue blood. You heard that right. Rather than iron-based hemoglobin to transfer oxygen, they use copper-based proteins instead, which turns their blood a bright blue color.
This unique physiological characteristic attracted the notice of the biomedical industry which uses the blue blood in research around bacterial endotoxins. Almost half a million horseshoe crabs are captured and bled annually for this purpose. The industry says it takes only about thirty percent of an individual crab’s blood before returning it to sea. I’m trying to imagine how likely I’d be ready to return to work the next day if someone bled me like this.
