If any further proof was needed of the vast unexplored wonders of the deep sea, this would fit the bill: researchers in New Zealand have discovered three new shark species that glow in the dark.
The study, published in the Frontiers in Marine Science journal, explains how the kitefin shark, the blackbelly lanternshark, and the southern lanternshark were found during a survey off the Chatham rise, an oceanic area off New Zealand's east coast, in January 2020.
Among the three glowing sharks, the kitefin shark is now the largest-known luminous underwater creature. The shark is usually found swimming 300 meters (984 feet) below sea level and preys on smaller sharks, ground fish and crustaceans.
Though light emission has been documented before in a range of aquatic life, including jellyfish and squids, the discovery is the first time scientists have been able to find proof of bioluminescence in sharks.
The study refers to the kitefin as a "giant luminous shark," and it can grow to 1.8 meters in length (almost 6 feet). But that comes way short of the 25-foot Great White shark featured in Steven Spielberg's "Jaws."
Led by marine biologists in Belgium and New Zealand, the study could change how we view life in the deep sea.
"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," said the study, published on Feb. 26.
The three new shark species all live in what is often called the ocean's "twilight zone," ranging between 200 and 1000 meters (3,200 feet) below sea level, beyond which solar light does not penetrate and is too weak to initiate photosynthesis.
Facing an environment with no place to hide, the sharks appear backlit against the bright surface of the water leading researchers to suggest that the sharks need the blue glowing camouflage to fend off potential predators and capture prey for survival.
Further research is required to uncover why the kitefin shark is luminescent given the species has few or no predators unlike the other two species recorded, the study said. Scientists speculate the slow-moving shark uses its natural glow to illuminate the ocean floor while it hunts for food, or to disguise itself while it approaches prey.