Leftvent
Encyclopedia
Leftvents are small, deep-sea lophiiform fish
comprising the family
Linophrynidae. Twenty-seven species
in five genera
are represented, distributed throughout tropical to subtropical waters of all oceans.
The name of the type genus Linophryne has been translated from the Greek
to mean "toad
that fishes
with a net
", an allusion to the fishes' impressive use of mimic
ry in luring prey. One of several families of anglerfish
es, the Linophrynidae are not well studied, and only one species is given a common name
: the netdevil
, Borophryne apogon. For this reason, the name "netdevil" can sometimes refer to any linophrynid.
line the jaw
s of a cavernous maw. An illicium (a modified dorsal spine; the "fishing rod
") — and an esca (a bulbous, bioluminescent
"fishing lure
") are present, also in females only. The illicium is shorter and the esca larger and complex compared to those found in some other anglerfish families, and its conformation is unique to each species. Most distinctively, Linophryne (the most diverse genus) and Borophryne species also possess greatly elongated and highly complex hyoid (chin) barbels
: these barbels are forked (with 3–5 main branches) and may be longer than the standard length of the fish, trailing below it in a tree-like manner. Sessile bioluminescent organs are also present on the branches of this barbel.
The complexity and length of the hyoid barbel varies widely among species, with some having no forkings. In Haplophryne barbels are absent altogether, and the illicium is reduced to a rounded flap.
Symbiotic
bacteria belonging to the family Vibrionaceae
are responsible for the luminescence; the strain
of bacteria is apparently different in each species. The bacteria are believed to originate from the surrounding seawater and colonise the organs via external ducts. The light produced is bluish to greenish, and the host female presumably has some control over its production.
Like other deep-sea anglers, leftvents have watery flesh and poorly ossified
bone
s; the skin, which in females is a dark brown to black in life (but colourless in Haplophryne), is extremely fragile and abrades with ease. Males are more or less colourless. Females possess strong sphenotic and preopercle spines and a highly distensible stomach
. Males, other than lacking lures, barbels, and (in most species) jaw teeth, have larger olfactory
organs and tubular eye
s; short and stout denticular teeth are also present. Sexual dimorphism
is extreme: females may reach a length of 23 centimetres (9.1 in), while males remain under 5 centimetres (2 in).
The pelvic fins and pelvic bone are absent in both sexes; the present fins are small and rounded. The dorsal fin
and anal fin are of roughly equal size, both positioned far back from the head, and retrorse.
and benthopelagic depths, ranging from 500 metres (1,640.4 ft) to 4000 metres (13,123.4 ft) below the ocean surface . Few details are known of their life history: mature females are poor swimmers and likely remain motionless much of the time, waiting for both mates and prey to approach their lures. The female's distensible stomach permits the ingestion of a wide variety of prey (lanternfish
are a common catch), even prey larger than the anglerfish herself. The diminutive males do not feed following their metamorphosis from larva
l to adult form: they are obligate parasites and exist only to provide sperm
to females. Males are believed to be attracted to females by the latter's species-specific lures and pheromone
s, which the males home in on with the help of their oversized olfactory organs and eyes.
Once a female is located, the male latches onto her with his otherwise useless teeth. Through enzymatic
processes, the tissues of the male gradually begin to coalesce with the tissues of the female, resulting in a permanent attachment and a shared circulatory system
, forming a hermaphroditic chimera
. The development of the male's large testes
— which was delayed prior to this point — begins, and all other organs in the male's body degenerate. Several males may thus attach to the same female with no apparent ill effects befalling her.
Leftvents are presumed to be non-guarders (that is, they do not care for eggs after release), with females releasing buoyant eggs
into the water, which become part of the zooplankton
; these may be contained within gelatinous rafts. The larvae remain near the shallower limits of the mesopelagic zone where they presumably feed on plankton and marine snow
. The larval epidermis is greatly inflated; this may help the larvae maintain neutral buoyancy
. Upon metamorphosis, the fish descend to deeper water. Males likely outnumber females by a wide margin, and physically mature more quickly, though as noted above they do not mature sexually until they attach to a female.
.gif)
There are 28 species in five genera:
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
comprising the 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...
Linophrynidae. Twenty-seven 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 five 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...
are represented, distributed throughout tropical to subtropical waters of all oceans.
The name of the type genus Linophryne has been translated 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;...
to mean "toad
Toad
A toad is any of a number of species of amphibians in the order Anura characterized by dry, leathery skin , short legs, and snoat-like parotoid glands...
that fishes
Fishing
Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
with a net
Net (device)
A net, in its primary meaning, comprises fibers woven in a grid-like structure, and is very infrequently mentioned in discussions of philosophy. It blocks the passage of large items, while letting small items and fluids pass...
", an allusion to the fishes' impressive use of mimic
Mimic
In evolutionary biology, mimicry is the similarity of one species to another which protects one or both. This similarity can be in appearance, behaviour, sound, scent and even location, with the mimics found in similar places to their models....
ry in luring prey. One of several families of 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...
es, the Linophrynidae are not well studied, and only one species is given a 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...
: the netdevil
NetDevil
NetDevil, owned by Gazillion Entertainment, was an American developer of massively multiplayer online role-playing games in Louisville, Colorado.- Beginnings :...
, Borophryne apogon. For this reason, the name "netdevil" can sometimes refer to any linophrynid.
Physical description
With roughly spherical to slightly elongate, gelatinous and scaleless bodies and large triangular heads, leftvents possess a body plan typical of deep-sea anglerfish. In females only, long, sharp fang-like teethTooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
line the jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
s of a cavernous maw. An illicium (a modified dorsal spine; the "fishing rod
Fishing rod
A fishing rod or a fishing pole is a tool used to catch fish, usually in conjunction with the pastime of angling, and can also be used in competition casting. . A length of fishing line is attached to a long, flexible rod or pole: one end terminates in a hook for catching the fish...
") — and an esca (a bulbous, bioluminescent
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...
"fishing lure
Fishing lure
A fishing lure is an object attached to the end of a fishing line which is designed to resemble and move like the prey of a fish. The purpose of the lure is to use movement, vibration, and colour to catch the fish's attention so it bites the hook...
") are present, also in females only. The illicium is shorter and the esca larger and complex compared to those found in some other anglerfish families, and its conformation is unique to each species. Most distinctively, Linophryne (the most diverse genus) and Borophryne species also possess greatly elongated and highly complex hyoid (chin) barbels
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...
: these barbels are forked (with 3–5 main branches) and may be longer than the standard length of the fish, trailing below it in a tree-like manner. Sessile bioluminescent organs are also present on the branches of this barbel.
The complexity and length of the hyoid barbel varies widely among species, with some having no forkings. In Haplophryne barbels are absent altogether, and the illicium is reduced to a rounded flap.
Symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
bacteria belonging to the family Vibrionaceae
Vibrionaceae
The Vibrionaceae are a family of Proteobacteria, given their own order. Inhabitants of fresh or salt water, several species are pathogenic, including the type species Vibrio cholerae, which is the agent responsible for cholera...
are responsible for the luminescence; the strain
Strain (biology)
In biology, a strain is a low-level taxonomic rank used in three related ways.-Microbiology and virology:A strain is a genetic variant or subtype of a micro-organism . For example, a "flu strain" is a certain biological form of the influenza or "flu" virus...
of bacteria is apparently different in each species. The bacteria are believed to originate from the surrounding seawater and colonise the organs via external ducts. The light produced is bluish to greenish, and the host female presumably has some control over its production.
Like other deep-sea anglers, leftvents have watery flesh and poorly ossified
Ossification
Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...
bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s; the skin, which in females is a dark brown to black in life (but colourless in Haplophryne), is extremely fragile and abrades with ease. Males are more or less colourless. Females possess strong sphenotic and preopercle spines and a highly distensible stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
. Males, other than lacking lures, barbels, and (in most species) jaw teeth, have larger olfactory
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
organs and tubular eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s; short and stout denticular teeth are also present. Sexual dimorphism
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:...
is extreme: females may reach a length of 23 centimetres (9.1 in), while males remain under 5 centimetres (2 in).
The pelvic fins and pelvic bone are absent in both sexes; the present fins are small and rounded. The 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...
and anal fin are of roughly equal size, both positioned far back from the head, and retrorse.
Life history
Adult leftvents have been trawled from both mesopelagicPelagic 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...
and benthopelagic depths, ranging from 500 metres (1,640.4 ft) to 4000 metres (13,123.4 ft) below the ocean surface . Few details are known of their life history: mature females are poor swimmers and likely remain motionless much of the time, waiting for both mates and prey to approach their lures. The female's distensible stomach permits the ingestion of a wide variety of prey (lanternfish
Lanternfish
Cooper Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence...
are a common catch), even prey larger than the anglerfish herself. The diminutive males do not feed following their metamorphosis from larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l to adult form: they are obligate parasites and exist only to provide sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
to females. Males are believed to be attracted to females by the latter's species-specific lures and pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
s, which the males home in on with the help of their oversized olfactory organs and eyes.
Once a female is located, the male latches onto her with his otherwise useless teeth. Through enzymatic
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
processes, the tissues of the male gradually begin to coalesce with the tissues of the female, resulting in a permanent attachment and a shared circulatory system
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
, forming a hermaphroditic chimera
Chimera (genetics)
A chimera or chimaera is a single organism that is composed of two or more different populations of genetically distinct cells that originated from different zygotes involved in sexual reproduction. If the different cells have emerged from the same zygote, the organism is called a mosaic...
. The development of the male's large testes
Testicle
The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...
— which was delayed prior to this point — begins, and all other organs in the male's body degenerate. Several males may thus attach to the same female with no apparent ill effects befalling her.
Leftvents are presumed to be non-guarders (that is, they do not care for eggs after release), with females releasing buoyant eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
into the water, which become part of the 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"...
; these may be contained within gelatinous rafts. The larvae remain near the shallower limits of the mesopelagic zone where they presumably feed on plankton and marine snow
Marine snow
In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below. The term was first coined by the explorer William Beebe as he...
. The larval epidermis is greatly inflated; this may help the larvae maintain neutral buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
. Upon metamorphosis, the fish descend to deeper water. Males likely outnumber females by a wide margin, and physically mature more quickly, though as noted above they do not mature sexually until they attach to a female.
Species
- Genus Acentrophryne
- Acentrophryne dolichonema Pietsch & Shimazaki, 2005.
- Acentrophryne longidens Regan, 1926.
- Genus Borophryne
- Netdevil, Borophryne apogon Regan, 1925.
- Genus Haplophryne
- Haplophryne mollisHaplophryne mollisThe soft leafvent angler, Haplophryne mollis, is a sexually dimorphic species of fish of the family Linophrynidae.-Reproduction:Some anglerfishes of the superfamily Ceratioidei employ an unusual mating method. Because individuals are presumably locally rare and encounters doubly so, finding a mate...
(Brauer, 1902). - Haplophryne triregium Whitley & Phillipps, 1939.
- Haplophryne mollis
- Genus Linophryne
- Linophryne algibarbata Waterman, 1939.
- Linophryne andersoni Gon, 1992.
- Linophryne arboriferaLinophryne arboriferaLinophryne arborifera, or illuminated netdevil, is an anglerfish of the family Linophrynidae, found in all tropical and subtropical oceans at depths below 1,000 m in the Bathyal zone. Its length is up to 77 mm...
Regan, 1925. - Linophryne arcturi (Beebe, 1926).
- Linophryne argyresca Regan & Trewavas, 1932.
- Linophryne bipennata Bertelsen, 1982.
- Linophryne brevibarbata Beebe, 1932.
- Linophryne coronata Parr, 1927.
- Linophryne densiramus Imai, 1941.
- Linophryne digitopogon Balushkin & Trunov, 1988.
- Linophryne escaramosa Bertelsen, 1982.
- Linophryne indica (Brauer, 1902).
- Linophryne lucifer Collett, 1886.
- Linophryne macrodon Regan, 1925.
- Linophryne maderensis Maul, 1961.
- Linophryne parini Bertelsen, 1980.
- Linophryne pennibarbata Bertelsen, 1980.
- Linophryne polypogon Regan, 1925.
- Linophryne quinqueramosa Beebe & Crane, 1947.
- Linophryne racemifera Regan & Trewavas, 1932.
- Linophryne sexfilis Bertelsen, 1973.
- Linophryne trewavasae Bertelsen, 1978.
- Genus Photocorynus
- Photocorynus spinicepsPhotocorynus spinicepsPhotocorynus spiniceps is a species of anglerfish in the family Linophrynidae. It is in the monotypic genus Photocorynus.The known mature male individuals are 6.2–7.3 millimeters , smaller than any other mature fish and vertebrate; the females, however, reach a significantly larger size of up...
Regan, 1925.
- Photocorynus spiniceps