''Gymnocephalus'' is a

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 ...

ray-finned fishes 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 ...

from 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 ...

Percidae The Percidae are a family of ray-finned fish, part of the order Perciformes, which are found in fresh and brackish waters of the Northern Hemisphere. The majority are Nearctic, but there are also Palearctic species. The family contains more than ...

, which includes the

perch Perch is a common name for fish of the genus ''Perca'', freshwater gamefish belonging to the family Percidae. The perch, of which three species occur in different geographical areas, lend their name to a large order of vertebrates: the Percif ...

es,

pike-perch ''Sander'' (formerly known as ''Stizostedion'') is a genus of predatory ray-finned fish in the Family (biology), family Percidae, which also includes the perches, Gymnocephalus, ruffes, and Darter (fish), darters. They are also known as "pike-pe ...

es and

darters The darters, anhingas, or snakebirds are mainly tropical waterbirds in the family Anhingidae, which contains a single genus, ''Anhinga''. There are four living species, three of which are very common and widespread while the fourth is rarer and ...

. They are from the

Western Palearctic The Western Palaearctic or Western Palearctic is part of the Palaearctic realm, one of the eight biogeographic realms dividing the Earth's surface. Because of its size, the Palaearctic is often divided for convenience into two, with Europe, North ...

area, although one species, ''

Gymnocephalus cernua The Eurasian ruffe (''Gymnocephalus cernua''), also known as ruffe or pope, is a freshwater fish found in temperate regions of Europe and northern Asia. It has been introduced into the Great Lakes of North America, reportedly with unfortun ...

'' has been accidentally introduced to the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

region where it is regarded as an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

. They have the common name "ruffe" and resemble the true

es in the genus ''Perca'', but are usually smaller and have a different pattern.

Characteristics

The species within the genus ''Gymnocephalus'' have a number of characters in common including that their

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s are not completely separate, they have enlarged canals extending from the

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

on their heads, the preorbital bone covers the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

ry bone, presence of setiform or bristle-like teeth, having very few or no vomerine and palatine teeth and the possession of three paired bones in the neck, known as extrascapulars, in their lateral line system, of which, two are simple tubes.

Species

There are currently five recognized species in this genus: * '' Gymnocephalus acerina'' ( J. F. Gmelin, 1789) (Donets ruffe) * ''

Gymnocephalus ambriaelacus ''Gymnocephalus ambriaelacus'' is a species of freshwater ray-finned fish, a ruffe, from the family Percidae which is endemic to Lake Ammersee, in the upper Danube basin in southern Germany. This species can reach a length is ( SL). The specie ...

'' Geiger & Schliewen, 2010 * '' Gymnocephalus baloni'' Holčík & K. Hensel, 1974 (Balon's ruffe) * ''

'' (

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 ...

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, 10th edition of ''Systema Naturae'', the sta ...

) (ruffe) * '' Gymnocephalus schraetser'' (

) (schraetzer)

Taxonomy

''Gymnocephalus'' was created by the

German German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...

physician A physician (American English), medical practitioner (Commonwealth English), medical doctor, or simply doctor, is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through th ...

and naturalist Marcus Elieser Bloch (1723-1799) with ''Perca schraester'' 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 ...

. It has traditionally been placed in 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 subfamily botanical names with "-oideae", and zoologi ...

Percinae alongside the true

of the genus ''Perca''. However, ''Gymnocephalus'' appears to be the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to both the Percinae and to the

Luciopercinae The Luciopercinae is a subfamily of ray-finned fish, classified within the Family (biology), family Percidae, the subfamily includes the pike-perches and zingels. The pike-perches of the genus ''Zander, Sander'' have an Holarctic distribution whi ...

. The 5th edition of ''

Fishes of the World ''Fishes of the World'' by the American ichthyologist Joseph S. Nelson (1937–2011) is a standard reference for fish systematics. Now in its fifth edition (2016), the work is a comprehensive overview of the diversity and classification of the ...

'' treats ''Gymnocephalus'' as the only genus in the

monotypic 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 "unispec ...

subfamily Acerinae, although Gill's Gymnocephalinae is referred to in some sources. The name of the genus is a compound of the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''gymno'' meaning "naked" and ''kephalos'' meaning "head". Within the genus molecular studies have shown that the ruffe ''G. cernua'' is sister to a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

consisting of the Danube ruff ''G. baloni'' and the schraetzer or striped ruffe ''G. schraetser'', and that these last two species originated from a common ancestor about 8 million years ago and it has also been suggested that the relatively newly described ''G. ambriaelacus'' may be

synonymous A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

with ''G. baloni''. ''G. acerina'' has not had its genetics sampled which would assist understanding of the genus's phlyogenetics.

Geographic distribution

The species in the genus ''Gymnocephalus'' are found in Europe and one species, ''G. cernua'' having been accidentally introduced to North America in ballast water, originating form the river

Elbe The Elbe (; cs, Labe ; nds, Ilv or ''Elv''; Upper and dsb, Łobjo) is one of the major rivers of Central Europe. It rises in the Giant Mountains of the northern Czech Republic before traversing much of Bohemia (western half of the Czech Repu ...

in Germany, near the mouth of the St Louis River in

Lake Superior Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...

. This species has also been introduced outside of its native range in Europe.

References

External links

* {{Taxonbar, from=Q927216 Percidae Taxonomy articles created by Polbot