SPIDERS HAVE BLUE BLOOD

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They might not be royals, but spiders have blue blood filling their bodies. Unlike mammals, which have rich red haemoglobin in their blood to transport oxygen around the body, spiders use a similar molecule called hemocyanin. Whereas haemoglobin uses iron atoms to bind with oxygen, hemocyanin uses copper to transport oxygen around the spider’s body. Hemocyanin also absorbs all wavelengths of light except for those at the shortest end of the spectrum, reflecting it to appear blue. Spiders share this trait with snails and octopuses.