A colorful, dual purpose display

by the largest known glowing shark.

As they prowl the oceans, sharks aren't just hunting. Some of them are glowing. And among them, researchers have found, is the largest glow-in-the-dark species with a spine - on land or sea - that has ever been found.

A new study has established that kitefin sharks - which grow to almost six feet in length - emit blue green light.

The scientists who led the study in an expedition off the coast of New Zealand also expanded the understanding of what makes several species of tiny, deep-swimming lantern sharks glow. 

Tiny lantern sharks were already known to be luminous tricksters. Blue green bioluminescent organs on their bellies help them blend in with blueish light from above, so they can avoid detection by larger predators while possibly illuminating shrimp and squid on the sea floor - their dinner table.

The glowing undercarriage may also advertise reproductive organs to mates, although researchers were unable to piun down what exactly triggers the shark's displays.

But they did find that displays are regulated by the hormone melatonin, though other, yet -to-be tested hormones may help. [Lesley Evans Ogden]


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