Scientists have found three glow-in-the-dark sharks off the coast of New Zealand. The kitefin shark, blackbelly lanternshark and southern lanternshark weren’t unknown to science. However, scientists had never seen them glow until recently. It’s the first time this phenomenon has been observed in larger sharks.

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Researchers found the glowing sharks at the Chatham Rise, a 1,000-meter deep area of ocean floor east of New Zealand, last January, according to a study published last week in Frontiers of Marine Science. Researchers from Université Catholique de Louvain in Belgium and the National Institute of Water and Atmospheric Research in New Zealand observed a blue glow on the three sharks’ ventral surface when they were in a fully dark environment. A fainter blue glow came from their dorsal fins as well as the lateral and dorsal areas.

Related: 10 fun and fascinating facts about sharks

Many marine animals emit bioluminescence, a distinct glow due to a chemical reaction in the body. An animal needs a molecule called luciferin, which produces light when it reacts with oxygen, to really shine. The reaction is even more impressive if the organism also produces the catalyst luciferase. Bioluminescent animals can regulate their brain processes and chemistry to control when they light up. This could be for mating or hunting purposes or to scare off predators.

What does a shark gain from gleaming? Scientists are speculating. While you might think that lighting up would make you stand out, the sharks’ bioluminescence can actually serve as camouflage. Say you’re swimming below the shark on a sunny day. If the shark lights up its belly, and the sun is shining above, you’d only see a shadow.

These three New Zealand species cruise the mesopelagic zone, between 200 and 1,000 meters in depth. Sunlight can reach a maximum of 1,000 meters, so this area is also called the twilight zone. There’s nowhere to hide in the twilight zone, so bioluminescent camo comes in handy.

The study’s authors concluded, “Bioluminescence has often been seen as a spectacular yet uncommon event at sea but considering the vastness of the deep sea and the occurrence of luminous organisms in this zone, it is now more and more obvious that producing light at depth must play an important role structuring the biggest ecosystem on our planet.”

+ Frontiers of Marine Science

Via The Guardian, Smithsonian and BBC

Image via Frontiers of Marine Science