The depths of the sea hide unimaginable mysteries and creatures never discovered. One such example is the black dragonfish, which swarms in deep waters and rises to the surface, wriggling its way to the surface in search of food and drawing the attention of fishermen. We’ve finally been able to see one in extreme detail, and its behavior is fascinating: when the light is turned off, the dragonfish literally turns on the light.
The science and other stuff to know
These creatures wander in the deep, dark, and murky tropical and subtropical waters. Females can measure up to 25 cm (10 in) and are jet black. Males are brownish and smaller. They live between 500 and 2,000 m (1,600-6,500 ft) deep and feed on organisms and small fish. Females come to the surface during the day to find food.
Perhaps their most striking feature is that dragonfish are bioluminescent animals. That is, they have organs capable of producing light called photophores.
A BBC video shows how a team of experts built a camera that is sensitive to the dim light emitted by the subocular organs of the fish. After turning off the lights, they get a surprise. Dragonfish don’t just have bioluminescent organs under their eyes, they’re everywhere! Its dainty little body lits up completely, making the onlookers jump in excitement.
Although biologists do not fully understand this mechanism, they consider that it may be a defensive action to stun a predator, a tool to increase vision in deep areas where light does not reach, or a tool to attract food.
The truth is that these animals put up a wonderful show. Imagine a layer of plankton—a small bioluminescent organism—on the sea surface, on a starry night, moving to the beat of the waves and illuminating it as if it were the reflection of the cosmos.
Bioluminescent creatures are the object of study for biologists. Blinking bacteria, flaming fungus, shimmering squid, and flashing fish are some of the most exciting examples.
The oxidation of the chemical luciferin, catalyzed by the enzyme luciferase, produces nearly all of the beautiful light that we are drawn to. Some species generate their own light, while others harbor bacteria that do it for them. Bioluminescent organisms glow and flash for numerous purposes, including repelling predators, attracting predators of their predators, seducing potential mates, and luring prey.
If you want to learn more about the intriguing nature of the aquatic kingdom and bioluminescence, we recommend the following videos: