The Kitefin shark is the world's largest glowing vertebrate.

The Kitefin shark (Dalatias licha) can grow up to 1.8 meters (5.9 feet) in length, making it the largest known bioluminescent vertebrate on Earth. This discovery was officially documented in a study published in the journal Frontiers in Marine Science in February 2021. Researchers from the Université Catholique de Louvain in Belgium and the National Institute of Water and Atmospheric Research (NIWA) in New Zealand confirmed this phenomenon.The shark inhabits the 'twilight zone' of the ocean, typically found at depths between 200 and 1,000 meters. At these depths, predators looking upward can easily spot the dark silhouettes of animals against the dim sunlight filtering down. To counter this, the Kitefin shark uses specialized light-emitting organs called photophores located primarily on its ventral (belly) side.This biological strategy is known as counter-illumination. By producing a blue glow that matches the intensity and color of the light from the surface, the shark effectively camouflages itself. This allows the relatively slow-moving shark to ambush prey or avoid larger predators. Unlike many other bioluminescent creatures that use light to attract mates or lure prey, the Kitefin shark uses it primarily as a cloaking device.