In the murky depths of the ocean twilight zone, it helps to bring a flashlight. With glowing blue-green lights embedded all over its body, the aptly-named lanternfish is well equipped for seeing and signaling in the dark. Special light-producing organs called photophores line its belly, helping the fish blend in with light-speckled water and confuse predators that might attack from below. This superpower is fairly common for deep-sea creatures, but lanternfish have the distinction of an extra row of photophores running down their sides. The arrangement and flashing pattern of these running lights are unique to each of the 245+ species of lanternfish, which suggests that they’re not just used to camouflage the animals, but also to communicate.
For the most diverse family of fish in the deep ocean, the ability to signal to others of their species is kind of like having a custom dating app to find their mates. Whatever their secret is, they’re doing something right: lanternfish account for 60% of all deep-sea fish, totalling about 600 million tons of biomass across the world’s oceans. Their sheer numbers make lanternfish an attractive target for commercial fishing in the waters between South Africa and Antarctica.
Most species of lanternfish make a nightly journey to the ocean surface, following zooplankton, their favorite snack. By sunrise, they return to the depths, regulating their buoyancy with gas-filled swim bladders. So many of them do this at once that they appear as a solid mass on modern sensors. Case in point: When scientists in the 1950s tried to measure ocean depth using newly-developed sonar technology, the entire sea floor seemed to rise at night across the globe.. After years of confusion, researchers finally realized that this “false bottom” was actually caused by sonar bouncing off millions of small, gas-filled fish—mostly lanternfish—during their nocturnal migration.This discovery also gave scientists important insight into the ocean twilight zone’s incredible abundance and biodiversity.
|Scientific Name||Varies: group is represented by more than 245 species|
|Size||Range from about 2 to 30 cm (0.8 to 11.8 inches) in length, with most being under 15 cm (5.9 in).|
|Discovery||T. N. Gill, 1893|
|Eats how?||Migrates to the surface waters at night to feed|
|Is eaten by?||Tuna, sharks, other deep-sea fish (including other lanternfish); whales, dolphins, salmon, penguins, jumbo squid|
|Bioluminescence||Yes: on its sides and face, depending on species.|