X is for Xiphosuran
Xiphosuran is an anthropod of the order Xiphosura which includes horseshoe crab and other extinct forms. I found this strange-looking creature at the shores of Snake Island in Palawan---it was the first time that I have seen a horseshoe crab (Carcinoscorpius rotundicaudia), I didn't think it was a living creature. I noticed the metallic look of its shell, thought it was a helmet of some kind. When it moved, I thought it was sea turtle but when I looked closely, the shell resembles that of a crab. Nobody can tell me at the time what this was called. When I came home, I showed this image to my brother and he said it's a mangrove horseshoe crab.
Despite its name, horseshoe crabs are more closely related to spiders and scorpions than to crabs. They live primarily in and around shallow ocean waters and occasionally come on shore for mating. Horseshoe crabs have no hemoglobin in their blood, they have hemocyanin to carry oxygen. Because of the copper present in hemocyanin, their blood is blue. Their blue blood is widely used in biomedical sciences for the development of drugs for diseases like mental exhaustion and gastroenteritis.
Considered by biologists as living fossils because they have remained practically unchanged in terms of shape and size for millions of years. Fossils of horseshoe crab have been dated to roughly 450 million years ago.
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