Melanocetidae: humpback anglerfish, Melanocetus johnsonii
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Anglerfishes are bony fishes in the order Lophiiformes.
An anglerfish has a head of enormous size, broad, flat and depressed, with the remainder of the body appearing merely like an appendage. Anglerfish may grow to a length of 200 cm (6.5 feet); specimens of 90 cm (3 ft.) are common. It's maximum weight is 30 kilos (1000 US ounces)
Anglerfishes are, for the most part, deep-sea fishes, though there are some families that have shallow-water representatives, including one, the frogfishes (family Antennariidae), that occurs only in shallow water. Examples of other anglerfish families that have some shallow water species are the goosefishes (family Lophiidae) and the batfishes (family Ogcocephalidae). These families also have deep water representatives. The deep-sea mid-water anglerfishes belong to the superfamily Ceratioidea.
The order was formerly known as Pediculati.
Anglerfishes are named for their characteristic method of predation, Angler being another word for fisherman. The anglerfish has three long filaments sprouting from the middle of its head; these are the detached and modified three first spines of the anterior dorsal fin. As with all anglerfish species, the longest filament is the first (the illicium). This first spine protudes above the fish's eyes, and terminates in an irregular growth of flesh (the esca) at the tip of the spine. The spine is movable in all directions, and the esca can be wiggled so as to resemble a prey animal, and thus to act as bait to lure other predators close enough for the anglerfish to devour them whole. The jaws are triggered in automatic reflex by contact with the tentacle. (The netdevil anglerfish has similar growths protruding from its chin as well.)
As most anglerfish live mainly in the oceans' aphotic zones, where the water is too deep for sunlight to penetrate, their predation relies on the "lure" being bioluminescent (via bacterial symbiosis). In a related adaptation, anglerfish are dull gray, dark brown or black, and are thus not visible either in their own light or in that of similarly luminescent prey.
The wide mouth extends all around the anterior circumference of the head, and both jaws are armed with bands of long pointed teeth, which are inclined inwards, and can be depressed so as to offer no impediment to an object gliding towards the stomach, but to prevent its escape from the mouth. The anglerfish is able to distend both its jaw and its stomach (its bones are thin and flexible) to enormous size, allowing it to swallow prey up to twice as large as its entire body.
Some benthic (bottom-dwelling) forms have arm-like pectoral fins which the fish use to walk along the ocean floor. The pectoral and ventral fins are so articulated as to perform the functions of feet, the fish being enabled to move, or rather to walk, on the bottom of the sea, where it generally hides itself in the sand or amongst sea-weed. All around its head and also along the body the skin bears fringed appendages resembling short fronds of sea-weed, a structure which, combined with the extraordinary faculty of assimilating the colour of the body to its surroundings, assists this fish greatly in concealing itself in places which it selects on account of the abundance of prey.
Some anglerfish have a unique mating method. Since individuals are rare and encounters doubly so, finding a mate is a problem, especially at a time when both individuals are ready to spawn. When scientists first started capturing ceratioid anglerfish, they noticed that all of the specimens were females. These individuals were a few inches in size and almost all of them had what appeared to be parasites attached to them. It turned out that these "parasites" were the remains of male ceratioids.
When a male of one of these species hatches, it is equipped with extremely well developed olfactory organs that detect scents in the water. They have no digestive system, and thus are unable to feed independently. They must find a female anglerfish, and quickly, or else they will die. The sensitive olfactory organs help him to detect the pheromones that signal the proximity of a female anglerfish. When he finds a female, he bites into her flank, and releases an enzyme which digests the skin of his mouth and her body, fusing the pair down to the blood vessel level. The male then atrophies into nothing more than a pair of gonads that release sperm in response to hormones in the female's bloodstream indicating egg release. This is an extreme example of sexual dimorphism. However, it ensures that when the female is ready to spawn, she has a mate immediately available.
The spawn of the angler is very remarkable. It consists of a thin sheet of transparent gelatinous material 2 or 3 ft. broad and 25 to 30 ft. in length. The eggs in this sheet are in a single layer, each in its own little cavity. The spawn is free in the sea. The larvae are free-swimming and have the pelvic fins elongated into filaments.
In Europe, the tail meat is widely used in cooking and is often compared to lobster tail in taste and texture. It is therefore sometimes referred to as "poor man's lobster." The anglerfish is a culinary speciality in certain Asian countries. In Japan each fish sells for as much as USD$150. The liver alone, considered a great delicacy, can cost USD$100.
- ^ "Lophiiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. February 2006 version. N.p.: FishBase, 2006.
- ^ a b Ramsey Doran. Deep sea anglerfish. Retrieved on 3 April 2006.
This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.