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The eelpouts are the
ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Zoarcidae. As the common name suggests, they are somewhat
eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 20 families, 164 genera, and about 1000 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...
-like in appearance. All of the 300
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
are marine and mostly bottom-dwelling, some at great depths. Eelpouts are predominantly found in the Northern Hemisphere. The Arctic, north Pacific and north Atlantic oceans have the highest concentration of species; however, species are found around the globe. They are conventionally placed in the "
perciform Perciformes (), also called the Acanthopteri, is an order or superorder of ray-finned fish in the clade Percomorpha. ''Perciformes'' means "perch-like". Among the well-known members of this group are perches and darters (Percidae), and also sea ...
" assemblage; in fact, the
Zoarcoidei Zoarcoidei is a suborder of marine ray-finned fishes belonging to the Order (biology), order Perciformes. The suborder includes the wolffishes, Pholidae, gunnels and eelpouts. The suborder includes about 400 species. These fishes are predominantl ...
seem to be specialized members of the
Gasterosteiformes Gasterosteoidei is a suborder of ray-finned fishes that includes the sticklebacks and relatives, the 5th edition of ''Fishes of the World'' classifies this suborder within the order Scorpaeniformes. Systematics Gasterosteoidei is treated as a ...
-
Scorpaeniformes The Scorpaeniformes are a diverse Order (biology), order of Actinopterygii, ray-finned fish, including the lionfishes and sculpins, but have also been called the Scleroparei. It is one of the five largest orders of bony fishes by number of spec ...
group of
Acanthopterygii Acanthopterygii (meaning "spiny-finned one") is a superorder of teleost, bony fishes in the class Actinopterygii. Members of this superorder are sometimes called ray-finned fishes for the characteristic sharp, bony rays in their fins; however th ...
. The largest member of the family is ''
Zoarces americanus The ocean pout (''Zoarces americanus'') is an eelpout in the family Zoarcidae. It is found in the Northwest Atlantic Ocean, off the coast of New England and eastern Canada. The fish has antifreeze proteins in its blood, giving it the ability to ...
'', which may reach 1.1 m in length. Other notable genera include ''
Lycodapus Lycodapus is a genus of marine ray-finned fishes belonging to the Family (biology), family Zoarcidae, the eelpouts. The species in this genus are found in the Pacific and Southern Oceans. Taxonomy ''Lycodapus'' was first proposed as a monospecifi ...
'' and ''
Gymnelus ''Gymnelus'' is a genus of small fish in the family Zoarcidae found in the Arctic Ocean, and adjacent parts of the North Pacific and North Atlantic. They are highly variable in color, which has resulted in the description of several taxa now cons ...
''.


Taxonomy

The eelpout family was first proposed as the family Zoarchidae in 1839 by the English naturalist
William Swainson William Swainson Fellow of the Linnean Society, FLS, Fellow of the Royal Society, FRS (8 October 1789 – 6 December 1855), was an English ornithologist, Malacology, malacologist, Conchology, conchologist, entomologist and artist. Life Swains ...
but the spelling was changed to Zoarcidae after the spelling of the genus Zoarces was corrected by Theodore Gill in 1861. The 5th edition of ''
Fishes of the World ''Fishes of the World'' is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of t ...
'' classifies this family within the
suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...
Zoarcoidei Zoarcoidei is a suborder of marine ray-finned fishes belonging to the Order (biology), order Perciformes. The suborder includes the wolffishes, Pholidae, gunnels and eelpouts. The suborder includes about 400 species. These fishes are predominantl ...
, within the order Scorpaeniformes. Other authorities classify this family in the
infraorder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classific ...
Zoarcales within the suborder Cottoidei of the
Perciformes Perciformes (), also called the Acanthopteri, is an order or superorder of ray-finned fish in the clade Percomorpha. ''Perciformes'' means " perch-like". Among the well-known members of this group are perches and darters ( Percidae), and als ...
because removing the Scorpaeniformes from the Perciformes renders that taxon non
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
. ''Fishes of the World'' mentions four subfamilies but does not assign genera to the subfamilies but these were set out in Anderson and Federov's Annotated Checklist and this has been followed by ''
FishBase FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.
'' and ''
Catalog of Fishes Catalog of Fishes is a comprehensive on-line database and reference work on the scientific names of fish species and genera. It is global in its scope and is hosted by the California Academy of Sciences. It has been compiled and is continuously up ...
''.


Evolution and adaptations

Eelpout species have evolved to efficiently give birth to future generations. They utilize demersal eggs, which are eggs that are deposited on the seafloor, and can be either free or connected to the substrate. These egg clusters can range from 9.2 mm, to 9.8 mm, which are the largest compared to any other marine egg cluster. It has been found that eelpouts grow larger and heavier in areas where the water is relatively shallow. In these areas, this species consumes molluscs, invertebrates, and small fish. The difference of biodiversity at varying depths has led to the evolution of distinct populations, connecting to the study that temperature might have a significant effect on them. Studies have shown that there are three large families of eelpout species; Zoarcidae, Stichaeidae, and Pholidae. These species have been thought to have evolved in northern, colder seas, each diverging off of each other at different points in time, millions of years ago. The notched-fin eelpout, which is commonly found in the Sea of Okhotsk, have shown researchers what the average length of an adult eelpout is, usually sitting between 21 and 26 cm long (females typically larger than males). Their size has been found to increase as the depth of water in which they have been studied lowers. They feed commonly on Gammarids (small, shrimp like organisms), Polychaetes (marine worms), and Bivalves (clams and muscles) on the seafloor.


Subfamilies and genera

The eelpouts are classified into four subfamilies and 61 genera with around 300 species: * subfamily
Gymnelinae Gymnelinae is a subfamily of marine ray-finned fish belonging to the family Zoarcidae, the eelpouts. Most species are found in the North Pacific Ocean but one genus is cosmopolitan, and another is endemic to the Southern Ocean. Taxonomy Gymenlin ...
Gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...
, 1863
** ''
Andriashevia ''Andriashevia'' is a monospecific genus of marine ray-finned fish belonging to the subfamiy Gymnelinae of the family Zoarcidae, the eelpouts, its only species is ''Andriasheevia aptera''. It is found in the northwestern Pacific Ocean, where it oc ...
'' Fedorov & Neelov, 1978 ** ''
Barbapellis The moose eelpout (''Barbapellis pterygalces'') is a species of zoarcid fish found in Southern Ocean. This species is only known from a single adult female specimen from off Terre Adélie. This species is the only known member of its genus G ...
'' Iglésias, Dettai & Ozouf-Costaz, 2012 ** '' Bilabria''
Schmidt Schmidt may refer to: * Schmidt (surname), including list of people and fictional characters with the surname * Schmidt (singer) (born 1990), German pop and jazz singer * Schmidt (lunar crater), a small lunar impact crater * Schmidt (Martian c ...
, 1936
** '' Davidijordania''
Popov Popov (; masculine), or Popova (; feminine), is a common Russian, Bulgarian, Macedonian and Serbian surname. Derived from a Slavonic word ''pop'' (, "priest"). The fourth most common Russian surname, it may refer to: * Alek Popov (born 1966) ...
, 1931
** ''
Ericandersonia ''Ericandersonia'' is a monospecific genus belonging to the family Zoarcidae, the eelpouts. The only species is ''Ericandersonia sagamia'', a deepwater fish in the family Zoarcidae. The genus and species were newly described in 2006. It was fou ...
'' Shinohara & Sakurai, 2006 ** '' Gymnelopsis'' Soldatov, 1922 ** ''
Gymnelus ''Gymnelus'' is a genus of small fish in the family Zoarcidae found in the Arctic Ocean, and adjacent parts of the North Pacific and North Atlantic. They are highly variable in color, which has resulted in the description of several taxa now cons ...
'' Reinhardt 1834 ** ''
Hadropareia ''Hadropareia'' is a genus of marine ray-finned fishes belonging to the family Zoarcidae, the eelpout The eelpouts are the ray-finned fish family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance. All of the 300 ...
'' Schmidt, 1904 ** '' Krusensterniella'' Schmidt, 1904 ** ''
Magadanichthys ''Magadanichthys'' is a monospecific genus of marine ray-finned fish. Its only species is ''Magadanichthys skopetsi'' which is found in the northwestern Pacific Ocean off the Russian Far East. ''Magadanichthys skopetsi'' is a small fish species b ...
'' Shinohara, Nazarkin & Chereshnev, 2006 ** ''
Melanostigma ''Melanostigma'' is a cosmopolitan genus of marine ray-finned fishes belonging to the family Zoarcidae, the eelpouts. The fishes in this genus are found all round the world. Species The following species are classified within the genus ''Melanosti ...
'' Günther, 1881 ** '' Nalbantichthys''
Schultz Schultz is a German and Dutch surname derived from ''Schultheiß'', meaning village headman or constable/sheriff in the medieval sense (akin to today's office of mayor). It has many variations, such as Schuldt, Schulte, Schulten, Schultes, Schul ...
, 1967
** '' Opaeophacus''
Bond Bond or bonds may refer to: Common meanings * Bond (finance), a type of debt security * Bail bond, a commercial third-party guarantor of surety bonds in the United States * Fidelity bond, a type of insurance policy for employers * Chemical bond, t ...
&
Stein Stein may refer to: Places Austria * Stein, a neighbourhood of Krems an der Donau, Lower Austria * Stein, Styria, a municipality in the district of Fürstenfeld, Styria * Stein (Lassing), a village in the district of Liezen, Styria * Stein a ...
, 1984
** '' Puzanovia'' Fedorov, 1975 ** ''
Seleniolycus ''Seleniolycus'' is a genus of marine ray-finned fishes belonging to the family Zoarcidae, the eelpouts. The fishes in this genus are found in the Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the souther ...
'' Anderson, 1988 * subfamily
Lycodinae Lycodinae is a subfamily of marine ray-finned fish belonging to the Family (biology), family Zoarcidae, the eelpouts. These eelpouts are found are in all the world's oceans, with a number of species being found off southern South America. Taxono ...
Gill, 1861 ** ''
Aiakas ''Aiakas'' is a genus of marine ray-finned fishes belonging to the family Zoarcidae the eelpouts. These fishes are found in the southwestern Atlantic Ocean. Taxonomy ''Aiakes'' was first proposed as a genus in 1974 by the Argentina based marine ...
'' Gosztonyi, 1977 ** ''
Argentinolycus ''Argentinolycus'' is a monospecific genus of marine ray-finned fish belonging to the family Zoarcidae, the eelpouts. Its only species is ''Argentinolycus elongatus'' which is found in coastal southern eastern South America. Taxonomy ''Argentinol ...
'' Matallanas & Corbella, 2012 ** ''
Austrolycus ''Austrolycus'' is a genus of marine ray-finned fishes belonging to the family Zoarcidae, the eelpouts. The two species in this genus are found in the southeastern Pacific Ocean and the western South Atlantic Ocean off southern South America and t ...
'' Regan, 1913 ** '' Bellingshausenia'' Matallanas, 2009 ** '' Bentartia'' Matallanas, 2010 ** '' Bothrocara''
Bean A bean is the seed of some plants in the legume family (Fabaceae) used as a vegetable for human consumption or animal feed. The seeds are often preserved through drying (a ''pulse''), but fresh beans are also sold. Dried beans are traditi ...
, 1890
** '' Bothrocarina''
Suvorov Count Alexander Vasilyevich Suvorov-Rymniksky, Prince of Italy () was a Russian general and military theorist in the service of the Russian Empire. Born in Moscow, he studied military history as a young boy and joined the Imperial Russian ...
, 1935
** '' Crossostomus'' Lahille, 1908 ** ''
Dadyanos ''Dadyanos'' is a monospecific genus of marine ray-finned fish belonging to the family Zoarcidae, the eelpout The eelpouts are the ray-finned fish family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance. All of ...
'' Whitley, 1951 ** ''
Derepodichthys The cuskpout (''Derepodichthys alepidotus'') is a species of marine ray-finned fish belonging to the family Zoarcidae, the eelpouts. It is the only species in the monospecific genus ''Derepodichthys'' and is found in the eastern North Pacific Oce ...
'' Gilbert, 1896 ** '' Dieidolycus'' Anderson, 1988 ** '' Eucryphycus'' Anderson, 1988 ** ''
Exechodontes ''Exechodontes'' is a monospecific genus of marine ray-finned fish belonging to the family Zoarcidae, the eelpout The eelpouts are the ray-finned fish family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance. All ...
'' DeWitt, 1977 ** '' Gosztonyia'' Matallanas, 2009 ** '' Hadropogonichthys'' Fedorov, 1982 ** ''
Iluocoetes ''Iluocoetes'' is a monospecific genus of marine ray-finned fish belonging to the family Zoarcidae, the eelpouts. The only species in the genus is ''Iluocoetes fimbriatus''. This species is found off southern South America, off Chile and Argentina ...
'' Jenyns, 1842 ** '' Japonolycodes'' Shinohara, Sakurai & Machida, 2002 ** ''
Letholycus ''Letholycus'' is a genus of marine ray-finned fishes belonging to the family Zoarcidae The eelpouts are the ray-finned fish family (biology), family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance. All of the ...
'' Anderson, 1988 ** '' Lycenchelys'' Gill, 1884 ** ''
Lycodapus Lycodapus is a genus of marine ray-finned fishes belonging to the Family (biology), family Zoarcidae, the eelpouts. The species in this genus are found in the Pacific and Southern Oceans. Taxonomy ''Lycodapus'' was first proposed as a monospecifi ...
'' Gilbert, 1890 ** ''
Lycodes ''Lycodes'' is a genus of zoarcid fish in the subfamily Lycodinae. It is the most species-rich genus in its taxonomic family as well as in the Arctic Ocean and adjacent waters. They occupy both shallow waters and deeper waters down to 3000 mete ...
'' Reinhardt, 1831 ** ''
Lycodichthys ''Lycodichthys'' is a genus of marine ray-finned fish belonging to the family Zoarcidae, the eelpouts. They are found in the Southern Ocean. Taxonomy ''Lycodichthys'' was first proposed as a monospecific genus in 1911 by the German zoologist Pau ...
''
Pappenheim Pappenheim is a town in the Weißenburg-Gunzenhausen district, in Bavaria, Germany. It is situated on the river Altmühl, south of Weißenburg in Bayern. History Historically, Pappenheim was a statelet within the Holy Roman Empire. It was ...
, 1911
** '' Lycodonus'' Goode & Bean, 1883 ** '' Lycogrammoides'' Soldatov &
Lindberg Lindberg is a municipality in the district of Regen in Bavaria in Germany in the immediate neighbourhood of the larger town Zwiesel. Location Lindberg lies in the Danube Forest (''Donau-Wald'') region in the middle of the Bavarian Forest on ...
, 1928
** ''
Lyconema The bearded eelpout (''Lyconema barbatum'') is a species of marine ray-finned fish belonging to the family Zoarcidae, the eelpouts. This species is the only species in the monospecific genus ''Lyconema''. It is found in the eastern Pacific Ocean. ...
'' Gilbert, 1896 ** '' Maynea''
Cunningham Cunningham is a surname of Scottish origin, see Clan Cunningham. Notable people sharing this surname A–C *Aaron Cunningham (born 1986), American baseball player * Abe Cunningham, American drummer *Adrian Cunningham (born 1960), Australian ...
, 1871
** ''
Notolycodes ''Notolycodes'' is a monospecific genus of marine ray-finned fish belonging to the family Zoarcidae, the eelpout The eelpouts are the ray-finned fish family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance. All ...
'' Gosztonyi, 1977 ** '' Oidiphorus'' McAllister & Rees 1964 ** '' Ophthalmolycus'' Regan, 1913 ** '' Pachycara'' Zugmayer. 1911 ** '' Patagolycus'' Matallanas & Corbella, 2012 ** ''
Petroschmidtia ''Petroschmidtia'' is a genus of marine ray-finned fishes belonging to the Family (biology), family Zoarcidae, the eelpouts. The species in this genus are placed in the genus ''Lycodes'' by ''FishBase'' but ''Catalog of Fishes'' recognises this a ...
'' Taranetz & Andriashev, 1934 ** '' Phucocoetes'' Jenyns, 1842 ** '' Piedrabuenia'' Gosztonyi, 1977 ** '' Plesienchelys'' Anderson, 1988 ** '' Pogonolycus''
Norman Norman or Normans may refer to: Ethnic and cultural identity * The Normans, a people partly descended from Norse Vikings who settled in the territory of Normandy in France in the 9th and 10th centuries ** People or things connected with the Norma ...
, 1937
** ''
Pyrolycus ''Pyrolycus'' is a genus of marine ray-finned fishes belonging to the subfamily Lycodinae, the eelpouts, within the family Zoarcidae The eelpouts are the ray-finned fish family (biology), family Zoarcidae. As the common name suggests, they are ...
'' Machida & Hashimoto, 2002 ** ''
Santelmoa ''Santelmoa'' is a genus of marine ray-finned fishes belongong to the family Zoarcidae, the eelpout The eelpouts are the ray-finned fish family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance. All of the 300 sp ...
'' Matallanas, 2010 ** ''
Taranetzella The loosekin eelpout (''Taranetzella lyoderma'') is a species of marine ray-finned fish belonging to the Family (biology), family Zoarcidae, the eelpouts. It is the only species in the monospecific genus ''Taranetzella''. This eelpout is found in ...
'' Andriashev, 1952 ** ''
Thermarces ''Thermarces'' is a genus of marine ray-finned fish belonging to the family Zoarcidae, the eelpouts. They are associated with hydrothermal vents and cold seeps at bathypelagic depths in the East Pacific and West Atlantic Ocean. Species The follo ...
'' Rosenblatt &
Cohen Cohen () is a surname of Jewish, Samaritan and Biblical origins (see: Kohen). It is a very common Jewish surname (the most common in Israel). Cohen is one of the four Samaritan last names that exist in the modern day. Many Jewish immigrants ente ...
, 1986
** '' Zestichthys''
Jordan Jordan, officially the Hashemite Kingdom of Jordan, is a country in the Southern Levant region of West Asia. Jordan is bordered by Syria to the north, Iraq to the east, Saudi Arabia to the south, and Israel and the occupied Palestinian ter ...
& Hubbs, 1925
* subfamily
Lycozarcinae ''Lycozoarces'' is a monospecific genus of marine ray-finned fish belonging to the family Zoarcidae, the eelpouts, its only species being ''Lycozoarces regani''. It is the only genus in the monogeneric subfamily Lycozoarinae. This taxon occurs in ...
Andriashev, 1939 ** '' Lycozoarces''
Popov Popov (; masculine), or Popova (; feminine), is a common Russian, Bulgarian, Macedonian and Serbian surname. Derived from a Slavonic word ''pop'' (, "priest"). The fourth most common Russian surname, it may refer to: * Alek Popov (born 1966) ...
, 1935
* subfamily
Zoarcinae ''Zoarces'' is a genus of marine ray-finned fishes belonging to the family Zoarcidae, the eelpouts. It is the only genus in the subfamily Zoarcinae. These eelpouts are found in the northern Atlantic and northern Pacific Oceans. Taxonomy ''Zoarce ...
Swainson, 1839 ** ''
Zoarces ''Zoarces'' is a genus of marine ray-finned fishes belonging to the family (biology), family Zoarcidae, the eelpouts. It is the only genus in the subfamily Zoarcinae. These eelpouts are found in the northern Atlantic and northern Pacific Oceans. ...
''
Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...
1829


Characteristics

The body of eelpouts is relatively elongated and laterally compressed. Their heads are relatively small and ovoid. Juveniles have a more rounded snout and relatively larger eye than adults. Their scales are absent or very small. The
dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...
and
anal Anal may refer to: Related to the anus *Related to the anus of animals: ** Anal fin, in fish anatomy ** Anal vein, in insect anatomy ** Anal scale, in reptile anatomy *Related to the human anus: ** Anal sex, a type of sexual activity involving ...
fins are continuous down their bodies up to their
caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into th ...
fin. They produce the pigment
biliverdin Biliverdin (from the Latin for green bile) is a green tetrapyrrolic bile pigment, and is a product of heme catabolism.Boron W, Boulpaep E. Medical Physiology: a cellular and molecular approach, 2005. 984–986. Elsevier Saunders, United States. ...
, which turns their bones green. This feature has no apparent evolutionary function and is harmless. Overall, there is no
sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
.


Biology

Little is known about eelpout populations because they often slip through nets in sampling studies, and because some species live in inaccessibly deep habitats. Though many stories of their generosity span many cultures. Species for which trophic ecology has been documented are typically, if not always, benthic scavengers or predators. At least one species has also adapted the ability to breathe air when out of water.


Timeline

ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-65.5 till:10 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:5 start:-65.5 ScaleMinor = unit:year increment:1 start:-65.5 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR value:claret id:ANK value:rgb(0.4,0.3,0.196) id:HER value:teal id:HAD value:green id:OMN value:blue id:black value:black id:white value:white id:cenozoic value:rgb(0.54,0.54,0.258) id:paleogene value:rgb(0.99,0.6,0.32) id:paleocene value:rgb(0.99,0.65,0.37) id:eocene value:rgb(0.99,0.71,0.42) id:oligocene value:rgb(0.99,0.75,0.48) id:neogene value:rgb(0.999999,0.9,0.1) id:miocene value:rgb(0.999999,0.999999,0) id:pliocene value:rgb(0.97,0.98,0.68) id:quaternary value:rgb(0.98,0.98,0.5) id:pleistocene value:rgb(0.999999,0.95,0.68) id:holocene value:rgb(0.999,0.95,0.88) BarData= bar:eratop bar:space bar:periodtop bar:space bar:NAM1 bar:NAM2 bar:space bar:period bar:space bar:era PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 shift:(7,-4) bar:periodtop from: -65.5 till: -55.8 color:paleocene text:
Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
from: -55.8 till: -33.9 color:eocene text:
Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
from: -33.9 till: -23.03 color:oligocene text:
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
from: -23.03 till: -5.332 color:miocene text:
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
from: -5.332 till: -2.588 color:pliocene text: Plio. from: -2.588 till: -0.0117 color:pleistocene text:
Pleist. The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
from: -0.0117 till: 0 color:holocene text: H. bar:eratop from: -65.5 till: -23.03 color:paleogene text:
Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...
from: -23.03 till: -2.588 color:neogene text:
Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...
from: -2.588 till: 0 color:quaternary text: Q. PlotData= align:left fontsize:M mark:(line,white) width:5 anchor:till align:left color:pliocene bar:NAM1 from: -5.332 till: 0 text:
Anarhichas ''Anarhichas'' is a genus of marine ray-finned fishes belonging to the Family (biology), family Anarhichadidae, the wolffishes or sea wolves. These fishes are found in the northern North Atlantic and North Pacific oceans. Taxonomy ''Anarhichas ...
color:pleistocene bar:NAM2 from: -2.588 till: 0 text:
Anarrhichthys The wolf eel (''Anarrhichthys ocellatus'') is a species of marine ray-finned fish belonging to the family ''Anarhichadidae'', the wolf fishes. It is found in the North Pacific Ocean. Despite its common name and resemblance, it is not a true eel ...
PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 bar:period from: -65.5 till: -55.8 color:paleocene text:
Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
from: -55.8 till: -33.9 color:eocene text:
Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
from: -33.9 till: -23.03 color:oligocene text:
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
from: -23.03 till: -5.332 color:miocene text:
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
from: -5.332 till: -2.588 color:pliocene text: Plio. from: -2.588 till: -0.0117 color:pleistocene text:
Pleist. The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
from: -0.0117 till: 0 color:holocene text: H. bar:era from: -65.5 till: -23.03 color:paleogene text:
Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...
from: -23.03 till: -2.588 color:neogene text:
Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...
from: -2.588 till: 0 color:quaternary text: Q.


Physiology


Metabolic adaptations to low temperatures

Species of eelpouts have adapted in order to grow and thrive in the extreme low temperatures of their habitats. The metabolic responses of Antarctic and temperate eelpout species during exercise and subsequent recovery at 0 °C is a point of emphasis when understanding this species. Contrary to the hypothesis of reduced glycolytic capacity in Antarctic fish as an adaptation to low temperatures, findings revealed similar increases in white muscle lactate, intracellular pH drop, and phosphocreatine depletion during strenuous exercise in both species. Notably, Antarctic eelpout exhibited faster recovery kinetics, including lactate clearance. This suggests a superior metabolic cold compensation mechanism compared to temperate eelpout. The study also proposed a correlation between reduced ATP energy content and muscular fatigue, highlighting the intricate metabolic adjustments crucial for sustaining activity in extreme cold conditions. These environmental factors surrounding this species show how it has adapted and survived over time.


Thermal stress responses

As global temperatures continue to rise, understanding how aquatic species adapt to thermal stress becomes increasingly crucial. The physiological responses of temperate eelpout (Zoarces viviparus) from the North Sea and Antarctic eelpout (Pachycara brachycephalum) to gradually increasing water temperatures were examined. The study explored parameters such as standard metabolic rate (SMR), intracellular pH regulation, and the upper critical temperature limit (TcII), to explain the species' thermal tolerance. Results revealed distinct differences in metabolic responses between the two species, indicating varied thermal sensitivities and adaptation strategies. The habitat of an eelpout can vary greatly throughout the year, as seasonal temperatures can change drastically between 3 and 12 degrees C. With increasing temperatures of the water in these regions, the eelpouts struggle to cope. Certain signs of this struggle are apparent when being studied in a lab, as they raise their pectoral fins, swim around more vigorously, and attempt to jump out of their holding aquariums, leading to the conclusion that higher temperatures lead to higher levels of agitation. For short periods of time, however, this species is able to cope. These findings have implications for understanding the physiological constraints faced by eelpout fish under thermal stress and offer insights into potential shifts in species distribution patterns driven by global warming.


References

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