Horseshoe crabs in a rack bleed into bottles at the BioWhittaker lab in Chincoteague Island, Va., Aug. 1, 2000. The blue blood is the only source of a compound used to test for contaminants in every drug and vaccine, every artificial limb, and every dialysis and intravenous drip. The crabs are returned to the sea the next day. (AP Photo/Steve Helber)

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