''Gymnocephalus'' is a genus of ray-finned fishes from the family Percidae, 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 Perci ...

es, pike-perches and darters. 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 region where it is regarded as an invasive species. 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 co ...

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 maxillary 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,

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 zoological ...

) (ruffe) * '' Gymnocephalus schraetser'' ( Linnaeus,

) (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 and naturalist Marcus Elieser Bloch (1723-1799) with ''Perca schraester'' as the type species. It has traditionally been placed in the subfamily Percinae alongside the true

of the genus ''Perca''. However, ''Gymnocephalus'' appears to be the sister taxon to both the Percinae and to the Luciopercinae. The 5th edition of '' Fishes of the World'' treats ''Gymnocephalus'' as the only genus in the monotypic subfamily Acerinae, although Gill's Gymnocephalinae is referred to in some sources. The name of the genus is a compound of the Greek ''gymno'' meaning "naked" and ''kephalos'' meaning "head". Within the genus molecular studies have shown that the ruffe ''G. cernua'' is sister to a clade 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 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 in Germany, near the mouth of the

St Louis River The Saint Louis River (abbreviated St. Louis River) is a river in the U.S. states of Minnesota and Wisconsin that flows into Lake Superior. The largest U.S. river to flow into the lake, it is in lengthU.S. Geological Survey. National Hydrography ...

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