Splitfin flashlightfish
| Diet | Very small animals called zooplankton |
|---|---|
| Size | Length: up to 13.7 inches (35 cm) |
| Type | Fishes |
| Range | West-Central Pacific Ocean |
| Habitat | Steep oceanic drop-offs around caves |
About the Splitfin flashlightfish
Flashlightfish shun the sun, hiding during the day in deeper reef waters. At night, they come out to feed, moving up reef walls to shallower areas. Eerie ice blue lights winking on and off—really light organs just under the fish's eyes—lure their tiny planktonic prey straight into their mouths.
Did you know?
- The flashlightfish is a bioluminescent species. They have an organ under each eye that emit a bluish light. This unusual organ gives them the common names lanterneye and flashlightfishes.
- The bioluminescent organ under the eye has a membrane that can be opened and closed, creating a blinking effect similar to an eyelid. One theory on the purpose of this blinking light is to confuse potential prey.
- This species is nocturnal. This means they are active at night, looking for food or mating, while resting during the day.
A pocketful of glowing bacteria
Animals that produce light are called bioluminescent. The light is usually blue, a wavelength that travels through water best and is visible to most marine organisms. Watch our splitfin flashlightfish. About every 30 seconds you'll see the flash of a fish's light organ. It's a bean-shaped pocket under either eye, filled with billions of symbiotic bacteria that live on sugar and oxygen from the fish's blood and emit a biochemical light as a by-product. Each pocket has a black membrane that can be raised, like an upside-down eyelid, to block nonstop illumination that could attract predators.
Blink to evade predators or attract a mate
When a school of flashlightfish is pursued by a predator, the fish use a “blink-and-run” defense. Taking off, the fish flash up to 75 times a minute and zigzag so that the predator can’t zero in on any individual. At some point, the school changes direction, the fish conceal their lights in unison, and they swim away safely. The light is also a visual Morse code for attracting a mate and for communicating within schools of 20 to 200 fish.