Docile creatures, horseshoe crabs are primarily concerned with snuffling up worms and molluscs from the sandy or muddy ocean shallows. They are loaded with eyes - a pair of lateral eyes as well as five other eyes are located on the top of the shell, photoreceptors line the tail, and ventral eyes are found near the mouth. This gives them light and UV sensitivity, keeping them in rhythm with the cycles of the days and nights, helping them find a mate, and serving to orient them, which helps when they swim upside down, angled a bit from horizontal.
Permit me a bit of latitude for today's post. As I am on holiday visiting family in Rhode Island, I am getting reacquainted with the creatures of the Northeast woodlands, and of course, the Atlantic. And when I ran across this "living fossil" down at the beach the other day, I knew I had to write a post about the critter whose story is as old as the hills, yet plays a crucial, but under-appreciated role in modern medicine. This is Limulus polyphemus, the Atlantic horseshoe crab, with three related species residing in East and Southeast Asia. As with other Arthropods, it is characterized by jointed appendages, a segmented body and an exoskeleton. The three main classes of Arthropods are the Insects, Crustaceans, and Arachnids, but the horseshoe crab merits its own class, called Merostomata, a term which refers to the positioning of the mouth at the center of it's ten legs. They also have a long, whip-like tail which gives it a menacing appearance, but serves as a means of flipping the crab upright in the event it is overturned. Docile creatures, horseshoe crabs are primarily concerned with snuffling up worms and molluscs from the sandy or muddy ocean shallows. They are loaded with eyes - a pair of lateral eyes as well as five other eyes are located on the top of the shell, photoreceptors line the tail, and ventral eyes are found near the mouth. This gives them light and UV sensitivity, keeping them in rhythm with the cycles of the days and nights, helping them find a mate, and serving to orient them, which helps when they swim upside down, angled a bit from horizontal. Few people realize, though, that the horseshoe crab may have saved their life, or that of a loved one. And it's done in cold blood. That's right: it's the horseshoe crab blood that is so important. First, it's blue, due to the presence of hemocyanin, but that's not the special thing. You see, horseshoe crab blood has certain components that are bacterial killers: clotting when they come in contact with bacteria endotoxins, binding with, and then deactivating them. Meanwhile, in labs around the world, the manufacturers of intravenous drugs, vaccines, and any medical device that needs to be implanted need to be sure their products are free of endotoxins, so that we can receive treatment without fear of potentially fatal sepsis. And so, the two worlds meet: an extract made from the horseshoe crab's blood, called LAL, is used to ensure the sterility of their products. If, for example, a vaccine batch tested with LAL gets slurry and clotty, it's not sterile, and is therefore discarded. To obtain this life-saving extract, the crabs are collected, transported, and bled (about 1/3 of their blood is removed). Happily, they can be returned to the ocean, though a certain percentage do not survive the ordeal. The importance of this marine invertebrate to the medical field may mean that more research is done to better understand and protect their populations.
3 Comments
I know this if off topic but I'm looking into starting my own blog and was wondering what all is required to get setup? I'm assuming having a blog like yours would cost a pretty penny? I'm not very web savvy so I'm not 100% certain. Any tips or advice would be greatly appreciated. Appreciate it
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Jeanne
6/23/2016 01:05:33 am
Hi,
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11/2/2020 04:07:26 am
This is really interesting, You’re a very skilled
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