Hanukkah, the Jewish festival of lights, begins at sundown tomorrow night. Like famed menorah this holiday commemorates, some fish have the ability to be lit from within. Using a process known as bioluminescence, they produce light internally by chemical reaction. This process has evolved in fish for a variety of reasons including:
- Camouflage from predators or prey with counterillumination,
- Unmasking other fish that have countershading,
- Distraction and confusion predators or prey, and
- Signaling to conspecificss (e.g., potential mates) or members of the same school.
The following festive fish would make even Clark Griswold jealous: they don’t need twinkle lights to help make their season bright!
Happy Holidays from The Fisheries Blog!
Splitfin flashlightfish (Anomalops katoptron)
A school of these megawatt fish are said to produce the brightest glow of any living organism – they can be seen from over 100 feet away. Their “flashlights” are large photophores, light producing organs, powered by symbiotic light-emitting bacteria. The flashlightfish can rotate their photophores to “turn off” their “flashlights.” They use these bright lights to signal to other flashlight fish, to attract prey, and also to evade predators by flashing their light in one direction then turning it off and swimming in another.
Velvet belly lantern shark (Etmopterus spinax)
Marine bioluminescence is almost exclusively blue in color because blue-green light transmits furthest in water (that’s why the ocean looks blue, especially deeper down) and blue bioluminescence helps “hide” fish in the blue water using counterillumination. More than ten percent of shark species are believed to be luminous. The velvet belly lantern shark is one of considerable note – its photophores run all along the underside of its body and create a substantial glow. With this countershading, the shark is almost invisible to fish below because its bioluminescence matches the ambient ocean light from above.
Shortnose greeneye (Chlorophthalmus agassizi)
While many fishes (like the velvet belly lantern shark) use blue bioluminescence as camouflage, shortnose greeneyes use their green bioluminescence to find those fish hiding in plain sight. They have a fluorescent green pigment in the lenses of their eye that allows them to distinguish between the shades of blue from counterillumination and those from the ocean.
Lanternfishes (family: Myctophidae)
Lanternfishes (myctophids) are a family of deep-sea fishes found across the globe. In fact, deep-sea trawl surveys indicate that this single family comprises as much as 65% of the fish biomass in the deep sea. Aptly named lanternfishes, all but one species in the family have photophores along their lateral and ventral sides in species-specific patterns. It is likely that these patterns are used to signal to potential mates. Some lanternfishes have very bright photophores near the base of their tails which are also believed to disorient predators with a blinding flash as the lanternfishes swim away to safetly.
Plainfin midshipman (Porichthys notatus)
For female plainfin midshipman, there’s nothing finer than a “man in uniform.” The species of toadfish is named for its four rows of photophores that resemble a naval uniform. Each fish has over 700 photophores which are used in luminous courtship displays.
Stoplight loosejaw (Malacosteus niger)
Stoplight loosejaws can produce red light and blue-green bioluminescence. In the deep-sea where they live, red light doesn’t travel very far. Stoplight loosejaws use their short distance red light to see prey in their immediate vicinity without drawing the attention of the prey or any of their own predators.
Which fish do you think is the most festive?