Eight-Armed Glowing Squid
Credit: Royal Society

The deep-sea eight-armed squid Taningia danae is the world's largest bioluminescent, or light-emitting, creature. The largest known specimen of the squid can grow up to 7.5 feet long and 130 pounds, with eyes the size of large grapefruits. The T. danae squid emits short, bright light flashes from large glowing organs at the tips of its tentacles. Researchers from Japan's National Science Museum in Tokyo speculate that these flashes might be used to blind prey or help the squids measure the distance to their targets in the dark depths of the sea.