Flabby whalefish
Encyclopedia
Flabby whalefishes are small, deep-sea cetomimiform fish
of the family Cetomimidae. They are among the most deep-living fish known, with some species recorded at depths in excess of 3.5 kilometres. Within the family are nine genera and 20 species. Juveniles are known as tapetails and were formerly thought to be in a separate family, dubbed Mirapinnidae. Adults exhibit extreme sexual dimorphism
, and the adult males were once thought to be exemplars of still another family, Megalomycteridae.
Thought to have a circumglobal distribution throughout the Southern Hemisphere
, flabby whalefish are the most diverse family of whalefishes. The largest species, Gyrinomimus grahami, reaches a length of some 40 centimetres. They are distinguished from other whalefishes by their loose, scaleless skin and lack of photophore
s.
system. Their eyes are either very small or vestigial, and it is instead this system of sensory pores (running the length of the body) which helps the whalefish to accurately perceive its surroundings by detecting vibrations. Named after the baleen
-whale-like bodies of adult females (from the Greek
ketos meaning "whale
" or "sea monster" and mimos meaning "imitative"), whalefish have large mouths, and the dorsal and anal fins are set far back of the head. All fins lack spines, and the pelvic fins are absent. The fish also lack swim bladders.
Flabby whalefish are a red to orange-brown colour in life, with the fins and jaws in particular being brightly coloured. This is explained by the fact that longer electromagnetic
wavelength
s (such as red and orange) do not penetrate into the whalefish's realm: animals which have evolved at this depth cannot see longer wavelengths, rendering the whalefish effectively black.
Their stomachs are highly distensible, allowing adult female whalefish to pursue prey otherwise too large for them to eat. Adult male members of the species do not eat at all, their jaws having fused shut during the transformation from their juvenile phase. Males retain the shells of prey consumed while still in the juvenile form, and continue to metabolise these shells through the remainder of their life. Both traits may have evolved due to extreme food scarcity in the ocean depths.
Though little is known regarding the life history of the flabby whalefish, new discoveries are being made. "[Whalefish] live in the oceanic bathypelagic realm (1000–4000m) [which is] a nutrient-poor habitat. Most fishes living there have pelagic larvae using the rich waters of the upper 200m. [The whalefish has remarkable] developmental changes and life-history strategies [that allow it to cope with occupying] such contrasting environments." This species is an "extreme example of ontogenetic metamorphoses and sexual dimorphism in vertebrates." In early 2009, the Royal Society published an article detailing the discovery "that three families with greatly differing morphologies, Mirapinnidae (tapetails), Megalomycteridae (bignose fishes) and Cetomimidae (whalefishes), are larvae, males and females, respectively, of a single family Cetomimidae." Apparently "morphological transformations involve dramatic changes in the skeleton, most spectacularly in the head, and are correlated with distinctly different feeding mechanisms. Larvae have small, upturned mouths and gorge on copepods. Females have huge gapes with long, horizontal jaws and specialized gill arches allowing them to capture larger prey. Males cease feeding, lose their stomach and oesophagus, and apparently convert the energy from the bolus
of copepods found in all transforming males to a massive liver that supports them throughout adult life."
Like many deep-sea fishes, flabby whalefish are thought to undergo nightly vertical migrations; they feed within the upper 700 metres of the water column by starlight, and retreat back to the abyssal depths by daybreak. Judging by the latest studies, the younger whalefish seem to frequent shallower water than adults.
Mirapinna, and
Parataeniophorus.
These "tapetails", as they are also known, had been known exclusively from immature specimens, which live in shallower waters than the adults.
The tapetails are named for their caudal fins, which include a narrow streamer that may be longer than the fish's body. The genus Mirapinna, known as the Hairyfish, lacks the streamer, but has multiple hair-like growths on its body. All mirapinnids lack scales and fin rays. Mirapinnids are all small fish, less than 7 centimetres (2.8 in) in length. They feed on small crustacean
s.
Family Mirapinnidae
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...
of the family Cetomimidae. They are among the most deep-living fish known, with some species recorded at depths in excess of 3.5 kilometres. Within the family are nine genera and 20 species. Juveniles are known as tapetails and were formerly thought to be in a separate family, dubbed Mirapinnidae. Adults exhibit extreme 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:...
, and the adult males were once thought to be exemplars of still another family, Megalomycteridae.
Thought to have a circumglobal distribution throughout the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
, flabby whalefish are the most diverse family of whalefishes. The largest species, Gyrinomimus grahami, reaches a length of some 40 centimetres. They are distinguished from other whalefishes by their loose, scaleless skin and lack 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.
Description
Living at extreme, lightless depths, adult female flabby whalefish have evolved an exceptionally well-developed lateral lineLateral 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...
system. Their eyes are either very small or vestigial, and it is instead this system of sensory pores (running the length of the body) which helps the whalefish to accurately perceive its surroundings by detecting vibrations. Named after the baleen
Baleen
Baleen or whalebone is a filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale's mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food...
-whale-like bodies of adult females (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;...
ketos meaning "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...
" or "sea monster" and mimos meaning "imitative"), whalefish have large mouths, and the dorsal and anal fins are set far back of the head. All fins lack spines, and the pelvic fins are absent. The fish also lack swim bladders.
Flabby whalefish are a red to orange-brown colour in life, with the fins and jaws in particular being brightly coloured. This is explained by the fact that longer electromagnetic
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s (such as red and orange) do not penetrate into the whalefish's realm: animals which have evolved at this depth cannot see longer wavelengths, rendering the whalefish effectively black.
Their stomachs are highly distensible, allowing adult female whalefish to pursue prey otherwise too large for them to eat. Adult male members of the species do not eat at all, their jaws having fused shut during the transformation from their juvenile phase. Males retain the shells of prey consumed while still in the juvenile form, and continue to metabolise these shells through the remainder of their life. Both traits may have evolved due to extreme food scarcity in the ocean depths.
Though little is known regarding the life history of the flabby whalefish, new discoveries are being made. "[Whalefish] live in the oceanic bathypelagic realm (1000–4000m) [which is] a nutrient-poor habitat. Most fishes living there have pelagic larvae using the rich waters of the upper 200m. [The whalefish has remarkable] developmental changes and life-history strategies [that allow it to cope with occupying] such contrasting environments." This species is an "extreme example of ontogenetic metamorphoses and sexual dimorphism in vertebrates." In early 2009, the Royal Society published an article detailing the discovery "that three families with greatly differing morphologies, Mirapinnidae (tapetails), Megalomycteridae (bignose fishes) and Cetomimidae (whalefishes), are larvae, males and females, respectively, of a single family Cetomimidae." Apparently "morphological transformations involve dramatic changes in the skeleton, most spectacularly in the head, and are correlated with distinctly different feeding mechanisms. Larvae have small, upturned mouths and gorge on copepods. Females have huge gapes with long, horizontal jaws and specialized gill arches allowing them to capture larger prey. Males cease feeding, lose their stomach and oesophagus, and apparently convert the energy from the bolus
Bolus
-Medicine:* Bolus , the administration of a drug, medication or other substance in the form of a single, large dose* Bolus , a tissue equivalent substance used in radiation therapy...
of copepods found in all transforming males to a massive liver that supports them throughout adult life."
Like many deep-sea fishes, flabby whalefish are thought to undergo nightly vertical migrations; they feed within the upper 700 metres of the water column by starlight, and retreat back to the abyssal depths by daybreak. Judging by the latest studies, the younger whalefish seem to frequent shallower water than adults.
Tapetails
Before a report released in January 2009, the juveniles of the species were thought to belong to a separate taxonomic family Mirapinnidae in the Cetomimiform order, with three genera Eutaeniophorus,Mirapinna, and
Parataeniophorus.
These "tapetails", as they are also known, had been known exclusively from immature specimens, which live in shallower waters than the adults.
The tapetails are named for their caudal fins, which include a narrow streamer that may be longer than the fish's body. The genus Mirapinna, known as the Hairyfish, lacks the streamer, but has multiple hair-like growths on its body. All mirapinnids lack scales and fin rays. Mirapinnids are all small fish, less than 7 centimetres (2.8 in) in length. They feed on small crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s.
Former classification
Three genera and five species of mirapinnid were documented, although the group remained obscure.Family Mirapinnidae
- Genus Eutaeniophorus
- Eutaeniophorus festivus - Festive ribbonfish
- Genus Mirapinna
- Mirapinna esau - Hairyfish
- Genus Parataeniophorus - Tapetails
- Parataeniophorus bertelseni
- Parataeniophorus brevis
- Parataeniophorus gulosus
Species
There are twenty species in nine genera:- Genus Cetichthys
- Cetichthys indagator (Rofen, 1959).
- Cetichthys parini Paxton, 1989.
- Genus Cetomimus
- Cetomimus compunctus Abe, Marumo & Kawaguchi, 1965.
- Cetomimus craneae Harry, 1952.
- Cetomimus gillii GoodeGeorge Brown GoodeGeorge Brown Goode , was an ichthyologist, although most of his time was spent as a museum administrator and he was very interested in the history of science, especially the history of the development of science in America. Goode graduated from Wesleyan University and studied at Harvard University...
& BeanTarleton Hoffman BeanTarleton Hoffman Bean was an American ichthyologist, born at Bainbridge, Pennsylvania on 8 October 1846. He died in Albany, New York on 28 December 1916.-FAMILY AND EDUCATION :...
, 1895.
- Cetomimus hempeli Maul, 1969.
- Cetomimus kerdops Parr, 1934.
- Cetomimus picklei (Gilchrist, 1922).
- Cetomimus teevani Harry, 1952.
- Genus Cetostoma
- Pink flabby whalefish, Cetostoma regani ZugmayerErich ZugmayerErich Johann Georg Zugmayer was an Austrian zoologist and ichthyologist-Species described by Zugmayer:* Benthalbella infans Zugmayer, 1911* Cetostoma regani Zugmayer, 1914...
, 1914.
- Pink flabby whalefish, Cetostoma regani Zugmayer
- Genus Danacetichthys
- Danacetichthys galathenus Paxton, 1989.
- Genus Ditropichthys
- Ditropichthys storeri (GoodeGeorge Brown GoodeGeorge Brown Goode , was an ichthyologist, although most of his time was spent as a museum administrator and he was very interested in the history of science, especially the history of the development of science in America. Goode graduated from Wesleyan University and studied at Harvard University...
& BeanTarleton Hoffman BeanTarleton Hoffman Bean was an American ichthyologist, born at Bainbridge, Pennsylvania on 8 October 1846. He died in Albany, New York on 28 December 1916.-FAMILY AND EDUCATION :...
, 1895).
- Ditropichthys storeri (Goode
- Genus GyrinomimusGyrinomimusGyrinomimus is a genus of flabby whalefishes in the family Cetomimidae.- Species :* Gyrinomimus andriashevi Fedorov, Balushkin & Trunov, 1987 * Gyrinomimus bruuni Rofen, 1959 * Gyrinomimus grahami Richardson & Garrick, 1964...
- Gyrinomimus andriashevi Fedorov, Balushkin & Trunov, 1987.
- Gyrinomimus bruuni Rofen, 1959.
- Gyrinomimus grahamiGyrinomimus grahamiGyrinomimus grahami is a flabby whalefish of the genus Gyrinomimus, found in all the southern oceans.-References:* Tony Ayling & Geoffrey Cox, Collins Guide to the Sea Fishes of New Zealand, ISBN 0-00-216987-8...
RichardsonJohn Richardson (naturalist)Sir John Richardson was a Scottish naval surgeon, naturalist and arctic explorer.Richardson was born at Dumfries. He studied medicine at Edinburgh University, and became a surgeon in the navy in 1807. He traveled with John Franklin in search of the Northwest Passage on the Coppermine Expedition of...
& Garrick, 1964. - Gyrinomimus myersi Parr, 1934.
- Gyrinomimus simplex Parr, 1946.
- Genus Notocetichthys
- Trunov southern cetomimid, Notocetichthys trunovi Balushkin, Fedorov & Paxton, 1989.
- Genus Procetichthys
- Procetichthys kreffti Paxton, 1989.
- Genus Rhamphocetichthys
- Savage's birdsnouted whalefish, Rhamphocetichthys savagei Paxton, 1989.