Lanternfish
Overview
Not to be confused with Lophiiformes Anglerfish
Anglerfish
Anglerfishes are members of the teleost order Lophiiformes . They are bony fishes named for their characteristic mode of predation, wherein a fleshy growth from the fish's head acts as a lure; this is considered analogous to angling.Some anglerfishes are pelagic , while others are benthic...

 (some of which have bioluminescent "lanterns" which grow from their foreheads).


Cooper Lanternfishes (or myctophids, from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 mykter, "nose" and ophis, "serpent") are small mesopelagic fish of the large family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Myctophidae. One of two families in the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Myctophiformes
Myctophiformes
Myctophiformes is an order of ray-finned fish consisting of two families of deep-sea marine fish, most notably the highly abundant lanternfishes...

, the Myctophidae are represented by 246 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in 33 genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, and are found in oceans worldwide.
Unanswered Questions
Encyclopedia
Not to be confused with Lophiiformes Anglerfish
Anglerfish
Anglerfishes are members of the teleost order Lophiiformes . They are bony fishes named for their characteristic mode of predation, wherein a fleshy growth from the fish's head acts as a lure; this is considered analogous to angling.Some anglerfishes are pelagic , while others are benthic...

 (some of which have bioluminescent "lanterns" which grow from their foreheads).


Cooper Lanternfishes (or myctophids, from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 mykter, "nose" and ophis, "serpent") are small mesopelagic fish of the large family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Myctophidae. One of two families in the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Myctophiformes
Myctophiformes
Myctophiformes is an order of ray-finned fish consisting of two families of deep-sea marine fish, most notably the highly abundant lanternfishes...

, the Myctophidae are represented by 246 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in 33 genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

. Their sister family, the Neoscopelidae
Neoscopelidae
The Neoscopelidae are a small family of deep sea fish closely related to the lanternfish. They are found in tropical and subtropical marine waters worldwide....

, are much fewer in number but superficially very similar; at least one neoscopelid shares the common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...

 'lanternfish': the large-scaled lantern fish, Neoscopelus macrolepidotus.

Sampling via deep trawling
Trawling
Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net that is used for trawling is called a trawl....

 indicates that lanternfish account for as much as 65% of all deep sea fish biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

. Indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, playing an important ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

 role as prey for larger organisms. With an estimated global biomass of 550 - 660 million metric tonnes, several times the entire world fisheries catch, lanternfish also account for much of the biomass responsible for the deep scattering layer
Deep scattering layer
The deep scattering layer, sometimes referred to as "The Sound Scattering Layer"; is the name given to a layer in the ocean consisting of a variety of marine animals. It was discovered through the use of sonar, as ships found a layer that scattered the sound and was thus sometimes mistaken for the...

 of the world's oceans. In the Southern Ocean
Southern Ocean
The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions...

, myctophids provide an alternative food resource to krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...

 for predators such as squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

 and the king penguin
King Penguin
The King Penguin is the second largest species of penguin at about , second only to the Emperor Penguin. There are two subspecies—A. p. patagonicus and A. p...

. Although plentiful and prolific, currently only a few commercial lanternfish fisheries
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...

 exist: limited operations off South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, in the sub-Antarctic, and in the Gulf of Oman
Gulf of Oman
The Gulf of Oman or Sea of Oman is a strait that connects the Arabian Sea with the Strait of Hormuz, which then runs to the Persian Gulf. It is generally included as a branch of the Persian Gulf, not as an arm of the Arabian Sea. On the north coast is Pakistan and Iran...

.

Description

Lanternfish typically have a slender, compressed body covered in small, silvery deciduous cycloid scale
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...

s (ctenoid in four species), a large bluntly rounded head, large elliptical to round lateral eyes (dorsolateral in Protomyctophum
Protomyctophum
Protomyctophum is a genus of lanternfish in the family Myctophidae.- Species :* Protomyctophum andriashevi Becker, 1963* Arctic telescope, Protomyctophum arcticum * Protomyctophum beckeri Wisner, 1971...

 species), and a large terminal mouth with jaws closely set with rows of small teeth. The fins are generally small, with a single high dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

, a forked caudal fin, and an adipose fin. The anal fin is supported by a cartilaginous
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 plate at its base, and originates under, or slightly behind, the rear part of the dorsal fin. The pectoral fins, usually with eight rays, may be large and well-developed to small and degenerate, or completely absent in a few species. In some species, such as those of the genus Lampanyctus
Lampanyctus
Lampanyctus is a genus of lanternfish in the family Myctophidae.- Species :* Spinytail lampfish, Lampanyctus acanthurus Wisner, 1974* Lampanyctus alatus Goode & Bean, 1896* Southern lanternfish, Lampanyctus australis Tåning, 1932...

, the pectorals are greatly elongated. Most lanternfish have a gas bladder
Gas bladder
The swim bladder, gas bladder, fish maw or air bladder is an internal gas-filled organ that contributes to the ability of a fish to control its buoyancy, and thus to stay at the current water depth without having to waste energy in swimming...

, but it degenerates or fills with lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

s during the maturation of a few species. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

 is uninterrupted.

In all but one species, Taaningichthys paurolychnus, a number of photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...

s (light-producing organs) are present; these are paired and concentrated in ventrolateral rows on the body and head. Some may also possess specialised photophores on the caudal peduncle, in proximity to the eyes (e.g., the "headlights" of Diaphus
Diaphus
Diaphus is a genus of lanternfish in the family Myctophidae.- Species :* Gilbert's large lantern fish, Diaphus adenomus Gilbert, 1905* Diaphus aliciae Fowler, 1934* Andersen's lantern fish, Diaphus anderseni Tåning, 1932...

 species), and luminous patches at the base of the fins. The photophores emit a weak blue, green, or yellow light, and are known to be arranged in species-specific patterns. In some species, the pattern varies
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

 between males and females. This is true for the luminous caudal patches, with the males' being typically above the tail and the females' being below the tail.

Lantern fish are generally small fish, ranging from about 2 centimetre (0.78740157480315 in) to 30 centimetres (11.8 in) in length, with most being under 15 centimetres (5.9 in). In life, shallow-living species are an iridescent
Iridescence
Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...

 blue to green or silver, while deeper-living species are dark brown to black.

Ecology

Lanternfish are well-known for their diel vertical migration
Diel vertical migration
Diel vertical migration, also known as diurnal vertical migration, is a pattern of movement that some organisms living in the ocean and in lakes undertake each day. Usually organisms move up to the epipelagic zone at night and return to the mesopelagic zone of the oceans or to the hypolimnion zone...

s: during daylight hours most species remain within the gloomy bathypelagic zone
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...

, between 300 metres (984.3 ft) and 1500 metres (4,921.3 ft) in depth, but towards sundown the fish begin to rise into the epipelagic zone, between 10-100 metres (33-330 feet) deep. The lanternfish are thought to do this to avoid predation, and because they are following the diel vertical migrations of zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...

, upon which the lanternfish feed. After a night spent feeding in the surface layers of the water column, the lanternfish begin to descend back into the lightless depths and are gone by daybreak.

Most species remain near to the coast, schooling
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...

 over the continental slope. Different species are known to segregate themselves by depth, forming dense, discrete conspecific layers, probably to avoid competition between different species. Due to the lanternfishes' gas bladders, these layers are visible on sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

 scans and give the impression of a "false bottom": this is the so-called deep-scattering layer that so perplexed early oceanographers
Oceanography
Oceanography , also called oceanology or marine science, is the branch of Earth science that studies the ocean...

.

There is great variability in migration patterns within the family. Some deeper-living species may not migrate at all, while others may do so only sporadically. Migration patterns may also be dependent on life history stage, sex, latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

, and season.

The arrangements of lanternfish photophores are different for each species, so it is assumed that their bioluminescence plays a role in communication
Animal communication
Animal communication is any behavior on the part of one animal that has an effect on the current or future behaviour of another animal. The study of animal communication, is sometimes called Zoosemiotics has played an important part in the...

, specifically in shoaling
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...

 and courtship
Courtship
Courtship is the period in a couple's relationship which precedes their engagement and marriage, or establishment of an agreed relationship of a more enduring kind. In courtship, a couple get to know each other and decide if there will be an engagement or other such agreement...

 behaviour. The concentration of the photophores on the flanks of the fish also indicate the light's use as camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...

; in a strategy termed counterillumination, the lanternfish regulate the brightness of the bluish light emitted by their photophores to match the ambient light level above, effectively masking the lanternfishes' silhouette when viewed from below.

A major source of food for many marine animals, lanternfish are an important link in the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

 of many local ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

s, being heavily preyed upon by whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...

s and dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...

s; large pelagic fish
Pelagic fish
Pelagic fish live near the surface or in the water column of coastal, ocean and lake waters, but not on the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and reef fish which are associated with coral reefs.The marine pelagic...

 such as salmon, tuna
Tuna
Tuna is a salt water fish from the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers, and some species are capable of speeds of . Unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red coloration derives from myoglobin, an...

 and shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s; grenadier
Rattail
Grenadiers or rattails are generally large, brown to black gadiform marine fish of the family Macrouridae...

s and other deep-sea fish (including other lanternfish); pinniped
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

s; sea birds, notably penguin
Penguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...

s; and large squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

 such as the jumbo squid, Dosidicus gigas. Lantern fish themselves have been found to feed on bits of plastic debris accumulating in the oceans. At least one lantern fish was found with over 80 pieces of plastic chips in its gut, according to scientists monitoring ocean plastic in the Pacific Ocean's Eastern Garbage Patch.
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