Photoblepharon palpebratum

Photoblepharon palpebratum, commonly known as the eyelight fish or one-fin flashlightfish, is a species of lanterneye fish from the Indo-Pacific (except the westernmost part, where replaced by the similar P. steinitzi). They are active at night, often feeding in large groups, and use the light to signal to other individuals, startle predators, and find small planktonic animals to feed on. Eyelight fish are sometimes seen at night by divers on steep reef faces. Daytime sightings are rare, as eyelight fish usually hide in caves during the day. The most characteristic feature of this small fish is the large light organ under each eye. The blue-green light can be turned on and off using a black membrane like an eyelid. The length of eyelight fish are up to 5 in (12cm) and they occur at ocean depths of 23-82 ft (7-25m).