Were it not for the one feature that practically qualifies these little guys for a part in a science fiction movie, the flashlight fish would be an easily overlooked, unremarkable little species.
Underneath their eyes these fish have a glowing pocket of bioluminescent bacteria that can be covered with an opaque “eye lid” at will, enabling them to emit flashes of light for a number of different purposes.
This amazing light can be seen from around 30 metres away. It is used to attract and locate the small crustaceans, polychaetes, and zooplankton on which they prey. It is also used for communication; these are social fish, usually found in pairs or small schools rather than alone. The females are territorial, seeing off invaders with a luminous threat display. This flashy behaviour is also applied in some nifty escape techniques, confusing potential predators by blinking their lights and then turning them off and swimming away quickly, leading predators to an empty pocket of water.
Many flashlight fish are deep-water dwellers, but Photoblepharon palpebratum lives at shallower depths, hiding in coral caves during the day and emerging at night to feed. They are found throughout the Indo-Pacific.
This article featured in Scuba Diver OCEAN PLANET (Issue 8/2014).