flashlight fish, Photoblepharon palpebratus

photo: Flickr user courtneyplatt

 Habitat: Indo-Pacific
Status: No Conservation Concerns
It’s rough living in the deep sea. It’s super cold, rather scary, and absolutely pitch black.  Luckily for the Flashlight Fish (Photoblepharon palpebratus) they never have to worry about the latter. Flashlight fish are aptly named for their large bean-shaped bioluminescent organs (a.k.a. photophores) under their eyes. To get that rockin’ glowing effect, luminous bacteria actually live in the organ create the light! It’s a symbiotic relationship in that the photophores glow in the dark, attracting zooplankton and small fish, on which the flashlight fish feed and the bacteria get the leftovers, so to speak. The light is also used for predator avoidance and for communication.
The light is actually constantly glowing but to turn it off the fish just rotates the organ in its eye socket so it is no longer visible. To “switch it back on” it just rotates the organ back into view. Flash on, flash off! 
Usually the lights flash about two to three times per minute but when threatened they can make it flash up to 50 to 70 times per minute! The fish also use a “blink and run” strategy to confuse predators by swimming quickly in one direction with the light on, zigzag, switch directions, and then turn the lights “off.” I can just see the predator being like OKAY OKAY ENOUGH ALREADY!

Some species move to shallow waters or coral during the night, but otherwise, they are exclusively deep water fish. They are typically about 14 centimetres (5.5 in) in adult length, although some species reach twice this size. That’s what you call a jumbo-sized flashlight fish.