@science: The kitefin shark (Dalatias licha), stretching nearly 1.8 meters (6 feet) long, has officially claimed the title of largest bioluminescent vertebrate known to science. Discovered glowing in New Zealand waters during a January 2020 deep-sea expedition, this ethereal predator emits a soft blue-green light that transforms the ocean's twilight zone into an alien dreamscape. Jérôme Mallefet from Belgium's Université Catholique de Louvain, who led the groundbreaking research published in Frontiers in Marine Science, described his first glimpse of the glowing giant: "I nearly cried when I saw it. It was so exciting." The shark's entire ventral surface and dorsal fins illuminate the darkness through specialized skin cells called photocytes, producing light at wavelengths between 455-486 nanometers—controlled by the hormone melatonin. Living between 200-600 meters deep in the ocean's "twilight zone," where sunlight barely penetrates, the kitefin shark joins two smaller glowing relatives—the blackbelly lanternshark and southern lanternshark—in this newly documented bioluminescent trinity. Unlike other glowing sea creatures that rely on bacterial symbiosis or luciferin-luciferase reactions, these sharks produce light through an entirely unknown mechanism that has baffled researchers. The evolutionary purpose remains mysterious. Scientists theorize the glow could serve as underwater camouflage, blending the shark's silhouette with faint surface light to avoid detection by predators below, or as a hunting tool to illuminate prey in the perpetual darkness. With an estimated 57 shark species potentially possessing bioluminescent abilities, this discovery suggests Earth's largest ecosystem—the deep ocean—may be far more luminous than previously imagined.

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