Decode the light on the shark's back

The lantern shark in the Atlantic and Pacific Ocean emits light from the spine so that enemies think they are dangerous animals.

Living in a depth of 200 to 1,000 meters under the ocean, lantern sharks (Etmopterus spinax) are small marine animals with cylindrical-like bodies. The body length of most mature lantern sharks is about 45cm, but some lengths can reach 60cm.

Scientists know very little about lantern sharks. They only know that they are capable of glowing like many species living in deep water. A previous study showed that lantern sharks possessed glowing cells (photophore) in the abdomen. They use light from their abdomen to disguise.

Light comes from the abdomen and spine of the lantern shark. (Photo: interestingfoto.com)

"Imagine you swim below the shark shark. Because of the light from the sun, you will see a dark area under the belly of the shark. If the shark's belly is also glowing, the dark space below them will turn away. Small fish often hide if they see the shadow of the lantern shark, but if the black shadow disappears, they will not know the shark is right above it, so the shark will have a chance to catch prey, " Dr. Julien Claes, a biologist of the Catholic University of Louvain in Belgium, said.

But a new study by Claes and colleagues demonstrates that the backbone of lantern sharks also luminescent thanks to cells that are capable of light, the BBC reported.

"Lantern sharks have two sharp spines and each spine is in front of a dorsal fin. Luminescent cells are just behind those bones," Claes said.

Tests show that predators can see light on shark's spine from a few meters away. In contrast, the prey of sharks only sees light at a distance of 1.5 m - the distance is too close, so the possibility of hiding is very low.

The team concludes that light on the back of the shark shark performs the function of threatening predators.

"That's how lantern sharks warn predators that they are prickly bones and attack them as foolish actions," Claes commented.