orderly-connections:

Flashlight Fishes

The name flashlight fishes usually refer to either the eyelight fish, Photoblepharon palpebratum, or the splitfin flashlight fish, Anomalops katoptron. Both are in the Beryciformes order of carnivorous, ray-finned fishes.

Photoblepharon palpebratum (left), Anomalops katoptron (right)

The most prominent feature of flashlight fishes are the large light organs present under each eye. Each sack contains colonies of bioluminescent bacteria which creates light simultaneously. The flashlight fishes are able to control the amount of light produced by either covering up the sack with a muscular flap, much like an eyelid or using rotational shutter-like mechanisms to rotate the sack inwards, essentially covering the light.

Photoblepharon palpebratum with its light organ open (left) and closed (right). Photo credit: Reef Builders

Commonly found in coral reefs and rocky regions of the eastern Indian and wider Pacific Oceans, it is one of the few shallow water species that can produce light. Predominantly nocturnal, they hide in caves and holes in the reef during the day. At night, they travel in schools far away from the reef surface, foraging for small planktonic prey for food.

It has been theorized that the light produced may help them locate and attract potential prey while allowing to communicate with other members of its species. They can also withdraw the light in the presence of predators to make a quick getaway