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.
Archerfish are renowned for their amazing ability to shoot water at prey. The fish have a narrow grove on the roof of its mouth, which the fish presses its tongue against to form a channel. It then contracts its gill covers to force water through the channel to form a jet up to 5m long.
An adult archerfish can reliably shoot prey up to 2m away. If the first jet does not knock the prey into the water, the fish will quickly fire a second shot. Accuracy is gained through experience, with young fish hunting in small schools to increase the chance that the prey is hit.
Most deep sea possess bioluminescent organs that are normally dependent on bacteria, maintained in special cells, for the production of the light.
The bacterial light is usually produced as a result of an enzyme (often luciferase) mediated oxidation reaction in which a molecule (often luciferan) changes its shape and emits a single photon of light in the process. Luciferan is a large complex molecule that can later be returned to its original shape through a reduction reaction during which it gains an amount of energy equivalent to the single photon of light it emitted earlier. Because the essential reaction is an oxidation reaction the host organism, in this case the fish, can control the amount of light emitted by controlling the blood flow, and hence the oxygen supply, to the cells containing the bacteria.
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