The viviparous eelpout (''Zoarces viviparus''), also known as the, viviparous blenny and European eelpout is species of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

belonging to the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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 roughly 300 species are ocean, marine and mostly bottom-dwelling, some at great depths. Eel ...

, the eelpouts. It is notable for being

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

and gives birth to live

larva A larva (; plural larvae ) 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. The ...

e (hence the description "mother of

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

s"). It is a common

soup Soup is a primarily liquid food, generally served warm or hot (but may be cool or cold), that is made by combining ingredients of meat or vegetables with stock, milk, or water. Hot soups are additionally characterized by boiling solid ing ...

ingredient in

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

countries. The bones are of greenish colour, due to a harmless pigment. Their skin is slimy and the colour is variable.

Taxonomy

The viviparous eelpout was first formally described as ''Blennius viviparus'' by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

in the 10th edition of his ''

Systema Naturae ' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomen ...

'' with its type locality given as "European seas". In 1829, the French

zoologist Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the Animal, animal kingdom, including the anatomy, structure, embryology, evolution, Biological clas ...

Georges 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". Cuvier ...

proposed the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Zoarces ''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 ''Zoarc ...

'' for the eelpouts and subsequently ''B, viviparus'' was descignated as the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of ''Zoarces'', possibly by

David Starr Jordan David Starr Jordan (January 19, 1851 – September 19, 1931) was the founding president of Stanford University, serving from 1891 to 1913. He was an ichthyologist during his research career. Prior to serving as president of Stanford Univer ...

in 1917/ The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''viviparus'' means "giving birth to live young", although the species is ovoviviparous.

Description

The viviparous eelpout has a slim, tapering body and resembles a small

burbot The burbot (''Lota lota'') is the only gadiform (cod-like) freshwater fish Freshwater fish are those that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 1.05%. These environments di ...

(''Lota lota''), a wide head and mouth and protuberant lips. It has long, ribbon-like dorsal and anal fins which continue on to unite with the arrowhead-shaped caudal fin. This distinguishes this fish from the two similar slim-bodied bottom-dwelling fish of the area, the

rock gunnel The rock gunnel (''Pholis gunnellus''), or butterfish, is a species of marine ray-finned fish belonging to the family Pholidae, the gunnels. This species is found in the coastal waters of the North Atlantic Ocean and in the Atlantic part of the Ar ...

(''Pholis gunnellus'') and the snake blenny (''Ophidion barbatum''). The bones are green. The tiny scales are embedded in the slimy skin. There dorsal fin becomes lower as it nears the caudal fin with these shorter rays being short and spinous. The colour is highly variable, although they are commonly greyish brown on the upper body and yellowish ventrally. They are marked with eithaer a single or double series of blotches along the body and on the dorsal fin. The pectoral fins have yellow or yellowish orange edges. This species reaches a maximum published

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

of , although is more typical, and may weigh up to .

Distribution and habitat

The viviparous eelpoutis found in the eastern Atlantic Ocean where its range extends from the

English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...

north around the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

, although it is absent from the Atlantic coasts of Ireland, eastrds onto the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

and northwards through the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

and along the coast of Norway to the

White Sea The White Sea (russian: Белое море, ''Béloye móre''; Karelian and fi, Vienanmeri, lit. Dvina Sea; yrk, Сэрако ямʼ, ''Serako yam'') is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is su ...

and the

Barents Sea The Barents Sea ( , also ; no, Barentshavet, ; russian: Баренцево море, Barentsevo More) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territo ...

. This species occurs in the intertidal zone where it can live in marine and brackish environments, avoiding drying out when exposed at low tide by sheltering beneath rocks or in fissures in the rock or by staying submerged in

rock pool A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. Many of these pools exist as separate bodies of water only at low tide. Many tide pool habitats are home to especially adaptable animals that ...

s. This

demersal fish Demersal fish, also known as groundfish, live and feed on or near the bottom of seas or lakes (the demersal zone).Walrond Carl . "Coastal fish - Fish of the open sea floor"Te Ara - the Encyclopedia of New Zealand. Updated 2 March 2009 They occ ...

is normally sedentary, hiding under rocks or among seaweed. Its can be found at depsth between , although it is normally found at depths of . Zoarces viviparus

Biology

The viviparous eelpout feeds on bottom-dwelling invertebrates, such as crustaceans, and fish eggs and fry. Adults mate during the months of August and September using

internal fertilisation Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For inter ...

. The fish are notably

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

, giving birth to 30–400 live developed young. Unusually, it does so during winter when water temperatures are extremely cold. Among fish it has one of the longest known pregnancies, lasting approximately six months. It has been discovered that the eelpout suckles its young embryos while still within their mother's body, making it the only

fish Fish are aquatic, craniate, gill-bearing 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. Approximately 95% of li ...

species to suckle its offspring. The embryos actually suckle from ovarian follicles, ingesting nutrients and gases from these internal structures. After depleting the egg's yolk reserves, the eelpouts attach their mouths to an ovarian follicle, which has a canal in its tip via which fluid and nutrients can flow. This follicle fluid is rich in proteins, fatty acids and glucose. It is also saturated in oxygen, which helps ventilate the gills of the developing fish. Each embryo latches onto a single follicle. This ensures an equal distribution of nutrients.

Utilisation

The viviparous eelpout is of minor commercial value to fisheries in some parts of its range.

References

{{Taxonbar, from=Q27336 Zoarces Fish described in 1758 Taxa named by Carl Linnaeus Fish of the Arctic Ocean Fish of the Atlantic Ocean Fish of the Baltic Sea Fish of the North Sea Fish of Europe Fish of Russia Viviparous fish