The anglerfish is a fish of the teleost order Lophiiformes (/ˌlɒfiɪˈfɔːrmiːz/). It is a bony fish named for its characteristic mode of predation, in which a fleshy growth from the fish's head (the esca or illicium) acts as a lure.
Some anglerfish are also notable for extreme sexual dimorphism and sexual symbiosis of the small male with the much larger female, seen in the suborder Ceratioidei. In these species, males may be several orders of magnitude smaller than females.
Anglerfish occur worldwide. Some are pelagic (dwelling away from the sea floor), while others are benthic (dwelling close to the sea floor); some live in the deep sea (e.g., Ceratiidae), while others on the continental shelf (e.g., the frogfishes Antennariidae and the monkfish/goosefish Lophiidae). Pelagic forms are most laterally compressed, whereas the benthic forms are often extremely dorsoventrally compressed (depressed), often with large upward-pointing mouths.
|Humpback anglerfish, Melanocetus johnsonii|
All anglerfish are carnivorous and are thus adapted for the capture of prey. Ranging in color from dark gray to dark brown, deep-sea species have large heads that bear enormous, crescent-shaped mouths full of long, fang-like teeth angled inward for efficient prey grabbing. Their length can vary from 2.0 cm (0.8 in) to 18.0 cm (7 in), but this is variation is largely due to sexual dimorphism with females being much larger than males. Frogfish and other shallow-water anglerfish species are ambush predators, and often appear camouflaged as rocks, sponges or seaweed. 
Most adult female ceratioid anglerfish have a luminescent organ called the esca at the tip of a modified dorsal ray (the illicium, or "fishing rod"). The organ has been hypothesized to serve the obvious purpose of luring prey in dark, deep-sea environments, but also serves to call males' attention to the females to facilitate mating.
The source of luminescence is symbiotic bacteria that dwell in and around the esca, enclosed in a cup-shaped reflector containing crystals, probably consisting of guanine. In some species, the bacteria recruited to the esca are incapable of luminescence independent of the anglerfish, suggesting they have developed a symbiotic relationship and the bacteria are unable to synthesize all of the chemicals necessary for luminescence on their own. They depend on the fish to make up the difference. Electron microscopy of these bacteria in some species reveals they are Gram-negative rods that lack capsules, spores, or flagella. They have double-layered cell walls and mesosomes. A pore connects the esca with the seawater, which enables the removal of dead bacteria and cellular waste, and allows the pH and tonicity of the culture medium to remain constant. This, as well as the constant temperature of the bathypelagic zone inhabited by these fish, is crucial for the long-term viability of bacterial cultures.
The light gland is always open to the exterior, so it is possible that the fish acquires the bacteria from the seawater. However, it appears that each species uses its own particular species of bacteria, and these bacteria have never been found in seawater. Haygood (1993) theorized that esca discharge bacteria during spawning and the bacteria are thereby transferred to the eggs.
In most species, a wide mouth extends all around the anterior circumference of the head, and bands of inwardly inclined teeth line both jaws. The teeth can be depressed so as to offer no impediment to an object gliding towards the stomach, but prevent its escape from the mouth. The anglerfish is able to distend both its jaw and its stomach, since its bones are thin and flexible, to enormous size, allowing it to swallow prey up to twice as large as its entire body.
In 2005, near Monterey, California, at 1474 metres depth, an ROV filmed a female ceratioid anglerfish of the genus Oneirodes for 24 minutes. When approached, the fish retreated rapidly, but in 74% of the video footage, it drifted passively, oriented at any angle. When advancing, it swam intermittently at a speed of 0.24 body lengths per second, beating its pectoral fins in-phase. The lethargic behaviour of this ambush predator is suited to the energy-poor environment of the deep sea.
Another in situ observation of three different whipnose anglerfish showed unusual upside-down swimming behavior. Fish were observed floating upside-down completely motionless with the illicium hanging down stiffly in a slight arch in front of the fish. The illicium was hanging over small visible burrows. It was suggested this is an effort to entice prey and an example of low-energy opportunistic foraging and predation. When the ROV approached the fish, they exhibited burst swimming, still upside-down.
The jaw and stomach of the anglerfish can extend to allow it to consume prey up to twice its size. Because of the small amount of food available in the anglerfish's environment this adaptation allows the anglerfish to store food when there is an abundance.
The name "anglerfish" derives from the species' characteristic method of predation. Anglerfish typically have at least one long filament sprouting from the middle of their heads, termed the illicium. The illicium is the detached and modified first three spines of the anterior dorsal fin. In most anglerfish species, the longest filament is the first. This first spine protrudes above the fish's eyes and terminates in an irregular growth of flesh (the esca), and can move in all directions. Anglerfish can wiggle the esca to make it resemble a prey animal, which lures the anglerfish's prey close enough for the anglerfish to devour them whole.
Some deep-sea anglerfish of the bathypelagic zone emit light from their esca to attract prey. This bioluminescence is a result of symbiosis with bacteria. The mechanism that ceratioids use to harness them is unknown, but researchers speculate that the bacteria enter the esca through small pores from seawater. Once inside, they multiply until their density is sufficient to produce a bright collective glow.
Because anglerfish are opportunistic foragers, they show a range of preferred prey with fish at the extremes of the size spectrum, whilst showing increased selectivity for certain prey. One study examining the stomach contents of threadfin anglerfish off the Pacific coast of Central America found these fish primarily ate two categories of benthic prey: crustaceans and teleost fish. The most frequent prey were pandalid shrimp. 52% of the stomachs examined were empty, supporting the observations that anglerfish are low energy consumers.
Some anglerfish, like those of the Ceratiidae, or sea devils employ an unusual mating method. Because individuals are locally rare, encounters are also very rare. Therefore, finding a mate is problematic. When scientists first started capturing ceratioid anglerfish, they noticed that all of the specimens were female. These individuals were a few centimetres in size and almost all of them had what appeared to be parasites attached to them. It turned out that these "parasites" were highly reduced male ceratioids. This indicates some taxa of anglerfish use a polyandrous mating system.
Certain ceratioids rely on parabiotic reproduction. Free-living males and unparasitized females in these species never have fully developed gonads. Thus, males never mature without attaching to a female, and die if they cannot find one. At birth, male ceratioids are already equipped with extremely well-developed olfactory organs that detect scents in the water. Males of some species also develop large, highly specialized eyes that may aid in identifying mates in dark environments. The male ceratioid lives solely to find and mate with a female. They are significantly smaller than a female anglerfish, and may have trouble finding food in the deep sea. Furthermore, growth of the alimentary canals of some males becomes stunted, preventing them from feeding. Some taxa have jaws that are never suitable or effective for prey capture. These features mean the male must quickly find a female anglerfish to prevent death. The sensitive olfactory organs help the male to detect the pheromones that signal the proximity of a female anglerfish.
However, the methods anglerfish use to locate mates vary. Some species have minute eyes that are unfit for identifying females, while others have underdeveloped nostrils, making them unlikely to effectively find females by smell. When a male finds a female, he bites into her skin, and releases an enzyme that digests the skin of his mouth and her body, fusing the pair down to the blood-vessel level. The male becomes dependent on the female host for survival by receiving nutrients via their shared circulatory system, and provides sperm to the female in return. After fusing, males increase in volume and become much larger relative to free-living males of the species. They live and remain reproductively functional as long as the female lives, and can take part in multiple spawnings. This extreme sexual dimorphism ensures that when the female is ready to spawn, she has a mate immediately available. Multiple males can be incorporated into a single individual female with up to eight males in some species, though some taxa appear to have a "one male per female" rule.
Symbiosis is not the only method of reproduction in anglerfish. In fact, many families, including the Melanocetidae, Himantolophidae, Diceratiidae, and Gigantactinidae, show no evidence of male symbiosis. Females in some of these species contain large, developed ovaries and free-living males have large testes, suggesting these sexually mature individuals may spawn during a temporary sexual attachment that does not involve fusion of tissue. Males in these species also have well-toothed jaws that are far more effective in hunting than those seen in symbiotic species.
Finally, sexual symbiosis may be an optional strategy in some species of anglerfishes. In the Oneirodidae, females carrying symbiotic males have been reported in Leptacanthichthys and Bertella—and others that were not still developed fully functional gonads. One theory suggests the males attach to females regardless of their own reproductive development if the female is not sexually mature, but when both male and female are mature, they spawn then separate.
|Angler Fish – YouTube|
|Weird Killer of the Deep – YouTube|
|The anglerfish: The original approach to deep-sea fishing – YouTube|
|3D scans reveal deep-sea anglerfish's huge final meal – YouTube|
One explanation for the evolution of sexual symbiosis is that the relatively low density of females in deep-sea environments leaves little opportunity for mate choice among anglerfish. Females remain large to accommodate fecundity, as is evidenced by their large ovaries and eggs. Males would be expected to shrink to reduce metabolic costs in resource-poor environments and would develop highly specialized female-finding abilities. If a male manages to find a female, then symbiotic attachment is ultimately more likely to improve lifetime fitness relative to free living, particularly when the prospect of finding future mates is poor. An additional advantage to symbiosis is that the male’s sperm can be used in multiple fertilizations, as he stays always available to the female for mating. Higher densities of male-female encounters might correlate with species that demonstrate facultative symbiosis or simply use a more traditional temporary contact mating.
The spawn of the anglerfish of the genus Lophius consists of a thin sheet of transparent gelatinous material 25 cm (10 in) wide and greater than 10 m (33 ft) long. The eggs in this sheet are in a single layer, each in its own cavity. The spawn is free in the sea. The larvae are free-swimming and have the pelvic fins elongated into filaments. Such an egg sheet is rare among fish.
Northwest European Lophius species are listed by the ICES as "outside safe biological limits". Additionally, anglerfish are known to occasionally rise to the surface during El Niño, leaving large groups of dead anglerfish floating on the surface.
In 2010, Greenpeace International added the American angler (Lophius americanus), the angler (Lophius piscatorius), and the black-bellied angler (Lophius budegassa) to its seafood red list—a list of fish commonly sold worldwide with a high likelihood of being sourced from unsustainable fisheries.
One family, the Lophiidae, is of commercial interest with fisheries found in western Europe, eastern North America, Africa, and East Asia. In Europe and North America, the tail meat of fish of the genus Lophius, known as monkfish or goosefish (North America), is widely used in cooking, and is often compared to lobster tail in taste and texture. In Asia, especially Korea and Japan, monkfish liver, known as ankimo, is considered a delicacy.
Others rely on the technique adopted by a wolf in sheep's clothing—they mimic a harmless species. ... Other predators even mimic their prey's prey: angler fish (Lophiiformes) and alligator snapping turtles Macroclemys temmincki can wriggle fleshy outgrowths of their fins or tongues and attract small predatory fish close to their mouths.
ceratioid males develop gigantic nostrils...relative to body size, some ceratioids have larger nasal organs than any other vertebrate
Black seadevils are small, deepsea lophiiform fishes of the family Melanocetidae. The five known species (with only two given common names) are all within the genus Melanocetus. They are found in tropical to temperate waters of the Atlantic, Indian, and Pacific Oceans, with one species known only from the Ross Sea.
One of several anglerfish families, black seadevils are named for their baleful appearance and typically pitch black skin. The family name Melanocetidae may be translated from the Greek melanos meaning "black", and cetus meaning either "whale" or "sea monster". The humpback anglerfish (Melanocetus johnsonii) was featured on the August 14, 1995, issue of Time magazine, becoming something of a flagship species of deepsea fauna.Canvey Island Monster
The Canvey Island Monster is the name given to an unusual creature whose carcass washed up on the shores of Canvey Island, England, in November 1953. A second, more intact, carcass was discovered in August 1954.
The 1953 specimen was described as being 76 cm (2.4 ft) long with thick reddish brown skin, bulging eyes and gills. It was also described as having hind legs with five-toed horseshoe-shaped feet with concave arches – which appeared to be suited for bipedal locomotion – but no forelimbs. Its remains were cremated after a cursory inspection by zoologists who said that it posed no danger to the public. The 1954 specimen was described as being similar to the first but much larger, being 120 cm (3.9 ft) long and weighing approximately 11.3 kg (25 lb). It was sufficiently fresh for its eyes, nostrils and teeth to be studied, though no official explanation was given at the time as to what it was or what happened to the carcass.
Some have speculated that the specimens may have been some type of anglerfish, whose fins had been mistaken for feet, while others have come to a more likely conclusion, that the specimens may have been frogfish, which do in fact walk on leg-like fins, have bulging eyes, and take on a variety of colours including reddish brown.In 1999, Fortean journalist Nicholas Warren carried out an investigation into the 1953–54 sightings. He was unable to locate any official records at the Plymouth Marine Biology Association Laboratory or the National Rivers Authority identifying the creature as being a known or unknown specimen, but was able to find accounts from locals who believed the creature was an anglerfish. This determination was later seconded by Alwyne Wheeler, former ichthyologist for the Department of Zoology at the British Natural History Museum, who put forward that the creature was an anglerfish whose pronounced fins had been incorrectly described as being hind legs.Deep sea fish
Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep sea fishes include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, viperfish, and some species of eelpout.
Only about 2% of known marine species inhabit the pelagic environment. This means that they live in the water column as opposed to the benthic organisms that live in or on the sea floor. Deep-sea organisms generally inhabit bathypelagic (1000–4000m deep) and abyssopelagic (4000–6000m deep) zones. However, characteristics of deep-sea organisms, such as bioluminescence can be seen in the mesopelagic (200–1000m deep) zone as well. The mesopelagic zone is the disphotic zone, meaning light there is minimal but still measurable. The oxygen minimum layer exists somewhere between a depth of 700m and 1000m deep depending on the place in the ocean. This area is also where nutrients are most abundant. The bathypelagic and abyssopelagic zones are aphotic, meaning that no light penetrates this area of the ocean. These zones make up about 75% of the inhabitable ocean space.The epipelagic zone (0–200m) is the area where light penetrates the water and photosynthesis occurs. This is also known as the photic zone. Because this typically extends only a few hundred meters below the water, the deep sea, about 90% of the ocean volume, is in darkness. The deep sea is also an extremely hostile environment, with temperatures that rarely exceed 3 °C (37.4 °F) and fall as low as −1.8 °C (28.76 °F) (with the exception of hydrothermal vent ecosystems that can exceed 350 °C, or 662 °F), low oxygen levels, and pressures between 20 and 1,000 atmospheres (between 2 and 100 megapascals).Double angler
Double anglers are a family, Diceratiidae, of anglerfishes. They are found in deep, lightless waters of the Atlantic, Indian and western Pacific Oceans.They are easily distinguished from other anglerfishes by their possession of a second light-bearing dorsal fin spine immediately behind the illicium (the bioluminescent lure present in other anglerfishes).
As in other anglerfishes, the male is very much smaller than the female, and after a larval and adolescent free-living stage, spends the rest of his life parasitically attached to a female.
Species in this family are known almost entirely from adolescent females; only two larvae, one adult female, and one adult male have been found.The first specimen of the two-rod anglerfish (first called Ceratias bispinosus) was collected during the expedition of HMS Challenger during 1873–1876. It was first described by Albert Günther in 1887 in volume 22 of "Report on the deep-sea fishes collected by H. M. S. Challenger during the years 1873–76. Report on the Scientific Results of the Voyage of ADD"Fish bone
Fish bone is any bone of a fish. Fish bone also includes the bony, delicate parts of the skeleton of bony fish, such as ribs and fin rays, but especially the ossification of connective tissue lying transversely inclined backwards to the ribs between the muscle segments and having no contact with the spine.
Not all fish have fish bones in this sense; for instance, eels and anglerfish do not.
There are several series of fish bones: Epineuralia, Epicentralia, Epipleuralia and Myorhabdoi.
Fish bones support the core muscles without inhibiting their motility.
In cuisine, fish bones are usually removed and not eaten. Because of their slim, tapered shape they may get caught in the windpipe and cause suffocation.Glauert's anglerfish
Glauert's anglerfish, Allenichthys glauerti, is an anglerfish that is in the monotypic genus, Allenichthys. It can grow to a length of 19 centimetres (7.5 in) TL and can be found in deep waters around Southern Australia.Goosefish
Goosefishes are anglerfishes in the family Lophiidae found in the Arctic, Atlantic, Indian, and Pacific Oceans, where they live on sandy and muddy bottoms of the continental shelf and continental slope, to depths of more than 1,000 m (3,300 ft).Like most other anglerfishes, they have a very large head with a large mouth that bears long, sharp, recurved teeth. Also like other anglerfishes, the first spine of the spinous dorsal fin has been modified as an angling apparatus (illicium) that bears a bulb-like or fleshy lure (esca). The angling apparatus is located at the tip of the snout just above the mouth and is used to attract prey. Lophiid anglerfishes also have two or three other dorsal fin spines located more posteriorly on the head, and a separate spinous dorsal fin with one to three spines located more posteriorly on the body just in front of the soft dorsal fin. In the more primitive anglerfish genera (Sladenia and Lophiodes), the gill opening extends partially in front of the elongated pectoral fin base. In the derived lophiid genera (Lophiomus and Lophius), and all other anglerfishes, the gill opening does not extend in front of the pectoral fin base. The largest individuals may exceed 1.5 m (4.9 ft) in length.Several of the large species in the genus Lophius, commonly known as monkfishes in northern Europe, are important commercially fished species. The liver of monkfish, known as ankimo, is considered a delicacy in Japan.Handfish
Handfish are any anglerfish within the family Brachionichthyidae, a group which comprises five genera and 14 extant species. These benthic marine fish are unusual in the way they propel themselves by walking on the sea floor rather than swimming.Haplophryne mollis
The ghostly seadevil or soft leftvent angler, Haplophryne mollis, is a species of anglerfish in the family Linophrynidae and is the only species in the genus Haplophryne. It is found in the bathypelagic and mesopelagic zones of tropical and subtropical parts of the world's oceans at depths down to about 2,250 m (7,400 ft).Humpback anglerfish
Melanocetus johnsonii is a species of black seadevils in the family of Melanocetidae, which means “black large sea creature” in Greek. It is named after James Yate Johnson after he discovered the fish in Madeira. The common names include humpback anglerfish, humpback blackdevil, and Johnson’s anglerfish.Lophius
Members of the genus Lophius, also sometimes called monkfish, fishing-frogs, frog-fish, and sea-devils, are various species of lophiid anglerfishes found in the Atlantic and Indian Oceans. Lophius is known as the "monk" or "monkfish" to the North Sea fishermen, a name which also belongs to Squatina squatina, the angelshark, a type of shark. The North European species is Lophius piscatorius, and the Mediterranean species is Lophius budegassa.Lophius americanus
Lophius americanus is a goosefish in the family Lophiidae, also called all-mouth, American anglerfish, bellows-fish, devil-fish, headfish, molligut, satchel-mouth, or wide-gape. It is native to the eastern coast of North America.Ogcocephalidae
Ogcocephalidae is a family of anglerfish specifically adapted for a benthic lifestyle of crawling about on the seafloor. Ogcocephalid anglerfish are sometimes referred to as batfishes, deep-sea batfishes, handfishes, and seabats. They are found in tropical and subtropical oceans worldwide. They are mostly found at depths between 200 and 3,000 m (660 and 9,840 ft), but have been recorded as deep as 4,000 m (13,000 ft). A few species live in much shallower coastal waters and exceptionally may enter river estuaries.They are dorsoventrally compressed fishes similar in appearance to rays, with a large circular, triangular, or box-shaped (in Coelophrys) head and a small tail. The largest members of the family are about 50 cm (20 in) in standard length. The illicium (a modified dorsal fin ray on the front of the head supporting the esca, a bulbous lure) can be retracted into an illicial cavity above the mouth. The esca is not luminous as in most other groups of anglerfishes, but secretes a fluid thought to act as a chemical lure, attracting prey. Analysis of their stomach contents indicates that batfishes feed on fish, crustaceans, and polychaete worms.Oneirodidae
The dreamers are a family, Oneirodidae, of deep-sea anglerfishes in the order Lophiiformes. They are the largest and most diverse group of deep-sea anglerfish, and also the least well known with several genera represented by only one, two, or three female specimens. They are found in deep, temperate waters around the world. They are small fishes, the largest species growing to about 20 cm (7.9 in) in total length.Percomorpha
The Percomorpha is a large clade of bony fish that includes the tuna, seahorses, gobies, cichlids, flatfish, wrasse, perches, anglerfish, and pufferfish.Photophore
A photophore is a glandular organ that 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. The bioluminescence can variously be produced from compounds during the digestion of prey, from specialized mitochondrial cells in the organism, called photocytes ("light producing" cells), or, similarly, associated with symbiotic bacteria in the organism that is cultured.
The character of photophores is important in the identification of deep sea fishes. Photophores on fish are used for attracting food or for camouflage from predators by counter-illumination.
Photophores are found on some cephalopods, including firefly squid, the sparkling enope or firefly squid, which can create impressive light displays.Prickly anglerfish
The prickly anglerfish (Himantolophus appelii) is a footballfish of the family Himantolophidae, found around the world in the southern oceans (apart from eastern Pacific), in deep water. Its length is up to 40 cm (16 in). It is a mesopelagic species.
Named in honour of Mr Appel who provided F. E. Clarke with a specimen.Rhycherus filamentosus
Rhycherus filamentosus, commonly known as the tasselled anglerfish, is a species of frogfish found in the southwestern Pacific Ocean where it is endemic to southern Australia. It is a well-camouflaged predator and lies in wait on the seabed for unwary prey to approach too close.Thaumatichthyidae
Thaumatichthyidae, the wolftrap anglers, is a small family of deep-sea anglerfishes, containing two genera and eight species found in all oceans. They are commonly known as wonderfish (a literal translation of Thaumatichthys), or wolftrap anglers or wolftrap seadevils because of their distinctive upper jaws with movable premaxillaries that can be lowered to form a cage-like trap around the much shorter lower jaw. They are related to (and were formerly placed within) the family Oneirodidae.