Sharks That Glow in the Dark: The Secret World of Bioluminescent Sharks

Sharks are often portrayed as powerful predators patrolling the oceans in silence, but some of the most fascinating species possess a secret that is invisible to the human eye. Deep beneath the waves, where sunlight barely reaches, certain sharks can produce their own glowing light. This natural phenomenon, known as bioluminescence, helps them communicate, camouflage themselves and even hunt in one of the darkest environments on Earth. Although these glowing sharks were only fully understood in recent decades, they have transformed scientists' understanding of deep-sea life. Their remarkable ability demonstrates that the ocean still holds countless mysteries waiting to be discovered.

Sharks That Glow in the Dark

The Science Behind Their Glow

Bioluminescence is the production of light through chemical reactions inside a living organism. While many people associate glowing creatures with jellyfish or fireflies, several shark species have evolved this remarkable ability as well.

Unlike fish that glow because of bacteria living on their skin, these sharks produce light using specialised cells called photophores. These tiny light-producing organs are embedded within their skin and can create soft blue-green light that travels efficiently through seawater.

Scientists believe sharks can carefully regulate the brightness of these photophores depending on their surroundings.

Which Sharks Can Glow?

One of the best-known glowing species is the kitefin shark (Dalatias licha), a deep-sea predator found in oceans around the world. In 2021, researchers confirmed that it is the largest known vertebrate capable of producing its own light.

Other glowing sharks include lanternsharks, blackbelly lanternsharks and southern lanternsharks. Most are relatively small and inhabit depths of several hundred metres where sunlight is extremely limited.

Because these sharks live so deep beneath the surface, many remained unknown to science until advances in underwater exploration made detailed observations possible.

Why Do Sharks Glow?

The primary purpose of bioluminescence appears to be camouflage. This strategy, known as counterillumination , helps sharks blend into the faint light filtering down from the surface.

Predators or prey looking upwards see the shark's glowing underside instead of a dark silhouette, making it much harder to detect.