This is the 兜蟹 - かぶとがに - Horseshoe crab.
Apart from being living fossils, they play an incredible role in medical applications that I did not know about. These creatures are so valuable, hopefully soon we won’t need to rely on their precious blood anymore.
(Section 4 of the Wiki article)
Harvest for blood
Horseshoe crabs use hemocyanin to carry oxygen through their blood. Because of the copper present in hemocyanin, their blood is blue.[37] Their blood contains amebocytes, which play a similar role to the white blood cells of vertebrates in defending the organism against pathogens. Amebocytes from the blood of L. polyphemus are used to make Limulus amebocyte lysate (LAL), which is used for the detection of bacterial endotoxins in medical applications



(even if I like crabs, shrimp and crayfish…but living fossils…>_> )





















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