This #SundayFishSketch comes from Ichthyologist, Rene Martin. Visit her shop on InPrint to see more of her artwork or to order prints!
Meet the Lanternfish
Lanternfish inhabit the mesopelagic zones of the worlds oceans and belong to the extensive family Myctophidae, consisting of nearly 250 species. As you might’ve guessed, Lanternfish earn their name for their spectacular display and use of bioluminescense—a trait shared by all but one Lanternfish, Taaningichthys paurolychnus.
Lanternfish are typically silvery and slender with a rounded head and proportionally massive eyes. Bioluminescent light is produced by specialized organs called photophores which are positioned in rows along the body and head. Some have photophores in other locations,such as the tail, right near the eyes, and on the fins. The color emitted varies between species—sometimes blue, yellow, or even green. More interestingly, the patterns at which the photophores are arranged are specific to certain species.
The Lanternfish is the most abundant type of fish in the deep-sea. According to some studies, they account for 65% of the biomass of the abyss. They’re also quite densely populated, at nearly one per cubic meter in the open ocean. Their wide dispersal around the planet and immense abundance—at 600 million metric tons worth globally—make them a vital to supporting ecosystems across the planet, often as a food source.
Despite their significant make-up of the oceans biomass, individual Lanternfish are pretty small—mostly less than 6 inches. The smallest of Lanternfish are just under an inch, but they can reach nearly a foot long in some species.
During the daytime, Lanternfish can be found anywhere between 1,000 to 5,000 feet deep, but as the sunsets, Lanternfish migrate epic distances to near surface levels—an impressive feat considering their size. They are thought to do this for a variety of reasons: 1) avoiding predators, and 2) following their own food—zooplankton.
Differing species of Lanternfish occupy differing layers of depth in the ocean and they do so by forming densely packed schools. The sheer density of these schools, aided by the gases in their swim bladders, are able to be picked up on sonar. This is the act at the center of the Deep-Scattering Layer phenomena which causes sonar to read these schools as false bottoms.
As interesting as that may be, the most spectacular thing about Lanternfish is unarguably their ability to produce light—but why do they do so to begin with?
Bioluminescence is thought to play a role in communication somehow, as is expected, but it also plays a role in camouflage. It is a strategy called counterillumination. Essentially the Lanterfish regulate how their light is emitted to match the ambient light reaching down to the depths from the surface as to confuse any predators.
So, there you have it—a fish you probably never heard of has one of the most clever camouflage tricks out there, accounts for 65% of the deep seas biomass, and disrupts sonar.
Sources
Hulley, P. Alexander (1998). Paxton, J.R.; Eschmeyer, W.N., eds. Encyclopedia of Fishes. San Diego: Academic Press. pp. 127–128. ISBN 0-12-547665-5.
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