''Agonus'' is a

monospecific genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

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 ...

belonging to the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Agoninae in the

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 ...

Agonidae Agonidae is a family of small, bottom-dwelling, cold-water marine fish. Common names for members of this family include poachers, Irish lords, sea ravens, alligatorfishes, starsnouts, hooknoses, and rockheads. They are notable for having elongate ...

. Its only species is ''Agonus cataphractus'', commonly known as the hooknose, pogge or armed bullhead. This is a

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 oc ...

found in the coastal waters of the northeastern Atlantic Ocean.

Taxonomy

''Agonus'' was first proposed as a genus in 1801 by the German

naturalists Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...

Marcus Elieser Bloch Marcus Elieser Bloch (1723–1799) was a German physician and naturalist who is best known for his contribution to ichthyology through his multi-volume catalog of plates illustrating the fishes of the world. Brought up in a Hebrew-speaking Jewish ...

and

Johann Gottlob Theaenus Schneider Johann Gottlob Theaenus Schneider (18 January 1750 – 12 January 1822) was a German Empire, German classicist and natural history, naturalist. Biography Schneider was born at Collm in Saxony. In 1774, on the recommendation of Christian Gottlob H ...

. Bloch and Schneider classified 4 species in ''Agonus'' and in 1814 Tilesius designated ''Cottus cataphractus'' as the

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

of the genus. ''Cottus cataphractus'' was described by

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

1758 Events January–March * January 1 – Swedish biologist Carl Linnaeus (Carl von Linné) publishes in Stockholm the first volume (''Animalia'') of the 10th edition of ''Systema Naturae'', the starting point of modern zoologic ...

with a type locality of Europe. The genus Agonus is now regarded as monotypic and is classified within the subfamily Agoninae in the family Agonidae.

Etymology

''Agonus'', the genus name, was not explained by Bloch and Schneider but may derive from the Greek ''agónos'', meaning "combat", referring to 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 ...

''cataphractus'' which means "clad in armour".

Description

''Agonus'' is characterised by the head and body having a complete covering of hard. bony plates, the plates on the body being jointed to enable the fish to move. There is a robust, curved spine on the lower edge of the operculum and another curved spine with two tips on the end of the snout. The ventral surface of the head bears numerous short

barbels In fish anatomy and turtle anatomy, a barbel is a slender, whisker like sensory organ near the mouth (sometimes called whiskers or tendrils). Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the z ...

. The first

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

is short based and is supported by 5 or 6 flexible spines, the second dorsal fin is longer based and contains between 6 and 8 soft rays, the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

is a similar shape to the second dorsal fin and contains between 5 and 7 soft rays. It has a slender tail with a small

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

at its end. The overall colour is dull brown on the upper body, marked with four dark dorsal saddles, with a pale lower body. The maximum published

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

is , although is more typical.

Distribution and habitat

''Agonus'' is found in coastal waters of the northeastern Atlantic Ocean where it is distributed from the southern

White Sea The White Sea (; Karelian language, Karelian and ; ) is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the nort ...

, also occurring around

Jan Mayen Jan Mayen () is a Norway, Norwegian volcanic island in the Arctic Ocean with no permanent population. It is long (southwest-northeast) and in area, partly covered by glaciers (an area of around the Beerenberg volcano). It has two parts: la ...

, and in the

Barents Sea The Barents Sea ( , also ; , ; ) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territorial waters.World Wildlife Fund, 2008. It was known earlier among Russi ...

Norwegian Sea The Norwegian Sea (; ; ) is a marginal sea, grouped with either the Atlantic Ocean or the Arctic Ocean, northwest of Norway between the North Sea and the Greenland Sea, adjoining the Barents Sea to the northeast. In the southwest, it is separate ...

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...

and in the

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

south to the

English Channel The English Channel, also known as the Channel, is an arm of the Atlantic Ocean that separates Southern England from northern France. It links to the southern part of the North Sea by the Strait of Dover at its northeastern end. It is the busi ...

. It typically is found in inshore waters, moving to deeper waters in winter in the

Skagerrak The Skagerrak (; , , ) is a strait running between the North Jutlandic Island of Denmark, the east coast of Norway and the west coast of Sweden, connecting the North Sea and the Kattegat sea. The Skagerrak contains some of the busiest shipping ...

, normally on sandy substrates, occasionally on bottoms with stones. It is found at depths of .

Biology

''Agonus'' feeds on small

crustaceans Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of Arthropod, arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquat ...

molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

brittle stars Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

and

worm Worms are many different distantly related bilateria, bilateral animals that typically have a long cylindrical tube-like body, no limb (anatomy), limbs, and usually no eyes. Worms vary in size from microscopic to over in length for marine ...

s. They spawn from February to May in the bases of kelps and whelks. The eggs take a long time to hatch. Very little else is known about the biology of this species.

References

External links

''Agonus cataphractus'' (Linnaeus, 1758)

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.

2015 {{Taxonbar, from2=Q2143094, from1=Q9142542 Agoninae Fish of the North Sea Fish described in 1758 Taxa named by Carl Linnaeus Monotypic ray-finned fish genera