Flashlightfish, Lanternfish And Other Deep Sea Wonders

The term flashlight fish can either refer to:

a family of fish, the Anomalopidae, also known as the lanterneye fish any one of a number of individual species, most but not all within that family, most commonly to the flashlight fish Photoblepharon steinitzi. The family Anomalopidae is in the order Beryciformes, the sawbellies. There are some unrelated fish that show similar phenomena to those that get the Anomalopidae their name, and some of these are also called flashlight fish. Notable among these are the lanternfish, of the family Myctophidae in the order Myctophiformes, of which there are over 200 species.

The following species are in the family Anomalopidae:

Splitfin flashlightfish, Anomalops katoptron, found in the warm waters of the western Pacific Ocean, sometimes in the very deep ocean trenches. Gulf flashlightfish, Phthanophaneron harveyi, found in the eastern Pacific Ocean and the Gulf of California Atlantic flashlightfish, Kryptophanaron alfredi, found in the Caribbean Parmops coruscans, found in the Eastern Pacific Ocean, and as far west as Tahiti and the Society Islands. Parmops echinatus, found in the Western Pacific Ocean, and as far east as Fiji. Eyelight fish Photoblepharon palpebratum Cook Islands flashlightfish, Protoblepharon rosenblatti, found near the Cook Islands Flashlight fish Photoblepharon steinitzi (sometimes regarded as a subspecies of P. palpebratusis), found in the Red Sea and eastern Indian Ocean Lanternfish sometimes known as flashlight fish include:

Chubby flashlight fish Electrona risso, found in the eastern Atlantic Ocean and the Mediterranean Sea Spotted lantern fish Myctophum punctatum, found in deep waters of the Mediterranean Sea The true flashlightfish, of the family Anomalopidae, have a luminous organ beneath the eyes; lanternfish have lights along its body. The light, which is red in colour and called bioluminescence, is generated by bacteria that live in special pouches. It is similar to the glow produced by fireflies.



Lanternfish (or myctophids, from the Greek words mykter, "nose" and ophis, "serpent") are small, deep sea fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, having a circumglobal distribution. They are aptly named after their conspicuous use of bioluminescence. Their sister family, the Neoscopelidae, are much fewer in number but superficially very similar; at least one neoscopelid shares the common name lanternfish: The large-scaled lantern fish (Neoscopelus macrolepidotus).

Sampling via deep trawling indicates that, together with the bristlemouths (Gonostomatidae) and lightfishes (Photichthyidae), lanternfish account for as much as 90% of all deep sea fish species. Indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. With an estimated global biomass of 550-660 million metric tonnes, lanternfish also account for much of the biomass responsible for the deep scattering layer of the world's oceans. Although plentiful and prolific, currently only a few commercial lanternfish fisheries exist: These include limited operations off South Africa, in the subantarctic, and in the Gulf of Oman.

Physical description Myctophid morphology is typified by a slender, compressed body covered in small, silvery deciduous cycloid scales (ctenoid in four species), a large bluntly rounded head, large elliptical to round lateral eyes (dorsolateral in Protomyctophum 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, an adipose fin, and an anal fin—supprted by a cartilaginous plate at its base—originating under or slightly behind the posterior end of the dorsal fin; the caudal fin is forked. The pectoral fins, usually with eight rays, may be large and well-developed to small and degenerate, or completely absent in a few species; the pectorals are greatly elongated in others, such as Lampanyctus species. The gas bladder is present in most lanternfish, but it degenerates or fills with lipids during the maturation of a few species. The lateral line is uninterrupted.

In all but one species (Taaningichthys paurolychnus), a number of photophores (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 close proximity to the eyes (e.g., the "headlights" of Diaphus species), and luminous patches at the base of the fins. The photophores—which emit a weak blue, green, or yellow light—are known to be arranged in species-specific patterns; some may also be sexually dimorphic in nature: this is true for the luminous caudal patches, with the males' being typically supracaudal (dorsal) and the females' being infracaudal (ventral). Lanternfish range in size from ca. 3–30 centimetres standard length, with most being under 15 centimetres. In life, shallow-living species are an iridescent blue to green or silver, while deeper-living species are dark brown to black.

Ecology Lanternfish are well-known for their diel vertical migrations: During daylight hours most species remain within the gloomy bathypelagic zone, between 300–1,200 metres depth; but towards sundown the fish begin to rise upwards into the epipelagic zone, between 10—100 metres depth. The lanternfish are thought to do this in order to avoid predation, and because they are following the diel vertical migrations of zooplankton 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 within close proximity to the coast, schooling over the continental slope. Different species are known to segregate themselves by depth, forming dense, discrete conspecific layers—this is believed to be a means of avoiding interspecies competition. Due to the lanternfishes' gas bladders, these layers are visible on sonar scans and give the impression of a "false bottom": This is the so-called deep-scattering layer that so perplexed early oceanographers.

It should be noted that 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, and season.

The arrangements of lanternfish photophores are different for each species, so it is assumed that their bioluminescence plays a role in intraspecies communication, specifically in shoaling behaviour and . The concentration of the photophores on the flanks of the fish also indicate the light's use as camouflage: 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 of many local ecosystems, being heavily preyed upon by: cetaceans, including whales and dolphins; large pelagic fish such as tuna and sharks; grenadiers and other deep-sea fish (including other lanternfish); pinnipeds; sea birds, notably penguins; and large squid such as the Jumbo Squid (Dosidicus gigas).

Reproduction An unidentified larval lanternfish with a large compliment of photophores. The lanternfish's deciduous scales were ablated during capture.All lanternfish are non-guarding pelagic spawners: That is, they release eggs and milt en masse into the water column, where fertilization takes place. The tiny eggs (0.70–0.90 millimetres in diameter, with a segmented yolk) are made buoyant by lipid droplets; the eggs, and later the hatched larvae (~2.0 millimetres), drift at the mercy of the currents until they have developed. Spawning may continue year-round in some species, but there is a peak during the winter-early spring season.

The study of lanternfish embryos is hampered by their extreme fragility: the chorion (outer membrane) often rupters during sampling. On the other hand, lanternfish are among the most well-studied as larvae: Species can be identified confidently by morphological characteristics (e.g., head, gut, and body shape), and with the exception of Diaphus species, from pigment (melanophore) patterns. Most larvae possess branchiostegal photophores while some species have a fuller compliment. Some species' larvae have eyes situated on stalks, for example the spotted lanternfish (Myctophum punctatum).

Lanternfish larvae are generally found in shallower waters than are adults. Larger species, such as the glacier lanternfish (Benthosema glaciale), may live for up to eight years (reaching maturity at 2-3 years). The smaller species, such as the Diogenes lanternfish (Diogenichthys laternatus) tend to have higher resiliences, doubling their populations within 15 months: Larger species may require up to five years. All have low fecundity, with females producing ca. 100-2,000 eggs per spawn, the number dependent on species and age.



Anglerfish (Cryptopasaras couesi): More commonly known as the "triplewart sea devil," the female has 3 luminescent sacs, called caruncles, in front of her dorsal fin. The caruncles also aid in enticing prey to within striking distances. The males are parasites and premanently attach themeselves to her sida to facilitate breeding.

Gulper (Eurypharynx pelecanoides): Also known as the "umbrellamouth gulper" or "the pelican eel," this fish can greatly expand its hinged jaws to engulf fishes and deposit them in its pouch-like lower jaw. These fish grow up to 2 feet long, including their whip-like tail , and live in depths greater than 6,500 feet.

Anglerfish (Melanocetus johnsoni): This fish is very round shaped with a large mouth. Nicknamed the "black whale" or "common black devil," its ferocious appearance is deceiving, since it can only reach a maximum length of 5 inches.

Viperfish (Chauliodus sloani): Its lower fangs are so long that they don’t even fit in its mouth!! Instead, they project back close to the eyes. No viperfish has ever been photographed in its natural habitat, but it is rumored to hover at a 45 degree angle.

Ogrefish (Anoplogaster cornuta): The juveniles differ so much from the adults of this species that it took over 50 years for biologists to realize that they were the same species. Also known as the "fangtooth," these animals are found in tropical and temperate waters up to 16,000 feet.

Gulper (Saccopharynx lavenberi): These animals can grow up to 6 feet long with rows of sharp teeth. They eat their prey whole, giving them the name "gulpers." Their victims travel to their "sack-gullet" and into the stomach where they are digested.

Anglerfish (Linophryne arborifera): Their Latin name means "toad that fishes with a net," which refers to the bioluminescent bulb on top of its head and the hanging filaments below that lure prey. Despite its ferocious jaws, this fish is only the size of a baby's fist.

Grammatostomias flagellibarba: Its name means "lined stomatid with a whip-barbel." This fish is only 6 inches long, but the barbel on its chin can project up to 6 feet long. In addition to its impressive barbel, it has two rows of blue-violet luminescent organs on its flanks, which can light up the dark depths of the ocean.

Vampyroteuthis infernalis: Also known as the "vampire squid from hell," this species has the largest eyes of any animal relative to its body size. A six inch squid has eyeballs the size of a large dog. This fish has wing-like fins and photophores, tiny lights on its body. These features help it find prey in depths of 3,000 feet.

Stylephorus chordatus: This fish can reach close to 3 feet in length. It has elongated tail rays, which give rise to its two nicknames "tube-eye" and "thread-tail." Its mouth is the most interesting feature, because it is able to expand up to 38 times its original size when sucking sea water.

Basket Star Fish (Gorgonocephalus arcticus): This fish can be found from the Arctic to Cape Cod and in water as deep as 4,000 feet. This fish is only about 20 inches long. It feeds by creating a canopy that grabs the food to the underside of the body where the mouth is located. The Latin name means "Gorgon Head."

Anglerfish (Caulophryne polynema): The name of this fish means "stalked toad with many filaments." It looks more like a porcupine. A fisherman who caught this fish thought it looked like it had swallowed an orange, because its stomach was so round and stretched. It can grow up to 8 inches long.

Anglerfish (Himantolophus groenlandicus): Sometimes called the "football fish," this animal looks like a linebacker for a professional football team. It was the first anglerfish ever found. This fish can grow up to 21 inches long.

Lasiognathus saccostoma: This fish has a huge overbite, which gave it the latin name meaning "grotesque among grotesques." It has a "fishing rod" on top of its head with a lure and three bony hooks, which serve to frighten away prey.

Thaumatichthys axeli: Also known as "Prince Axel’s wonder-fish," this fish has a bioluminescent organ projecting from its toothy jaws. This serves to light the dark habitat for this bottom-dweller, who lives in depths of up to 11,778 feet. The fish shown in the photograph was found in the Atlantic Ocean.

Long Nosed Chimaera (Harriotta raleighana): This fish has a sharp nose that resembles the nose contour of a supersonic jet aircraft (or maybe even an elephant!). It was for this reason that they were nicknamed "rattail" and "ghost shark." Long Nosed Chimaera have a dorsal fin with a venomous spine that could kill a person. Although this is not likely to happen because they live in waters 8,000 feet deep.

From PBS LIFE IN THE ABYSS

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