Sander (genus)

''Sander'' (formerly known as ''Stizostedion'') is a genus of predatory ray-finned fish in the family Percidae, which also includes the perches, ruffes, and darters. They are also known as "pike-perch" because of their resemblance to fish in the unrelated Esocidae (pike) family. They are the only genus in the monotypic tribe Luciopercini, which is one of two tribes in the subfamily Luciopercinae.

The earliest known fossils of this genus are partial jaw and vertebrae elements from the middle Miocene (Barstovian)-aged Wood Mountain Formation of Saskatchewan, Canada.

Characteristics

''Sander'' species have elongated and laterally compressed bodies and they range in total length from in the Volga pikeperch (''S. volgensis'') to in the zander (''S. lucioperca''). The species within the genus share canine-like teeth that are at their largest in the zander, and although they are not present in adult Volga pikeperches, they do possess them as juveniles. in addition, they have thin rows of teeth on their jaws, vomer, and palatines, the preopercle shows strong serrations along its edges, a continuous lateral line reaches all the way from the head to the caudal fin, and this is flanked by additional lateral lines, one each on the upper and lower lobes of the deeply forked caudal fin. Further features in common include the absence of genital papillae, seven or eight branchiostegal rays, 12–13 soft rays in the anal fin, and the eye has a reflective layer behind the retina, known as a tapetum lucidum, which is an adaptation for seeing in low-light conditions. The species in the genus ''Sander'' are largely piscivorous as adults.

Species

The genus includes these species:
* '' Sander canadensis'' Griffith & Smith, 1834 (sauger)
* '' Sander lucioperca'' Linnaeus, 1758 (zander)
* '' Sander marinus'' G. Cuvier, 1828 (estuarine perch)
* ''Sander vitreus'' Mitchill, 1818 (walleye)
* '' Sander volgensis'' J. F. Gmelin, 1789 (Volga pikeperch)
The fossil species '' Sander svetovidovi'' Kovalchuk, 2015 is known from the Late Miocene of Ukraine.

Phylogeny

Phylogenetic relationships of the species of genus ''Sander'' based on the concatenated data set of six gene regions and a Bayesian analysis. '' Romanichthys valsanicola'' is the nearest living relative of the genus ''Sander'' and is used as an outgroup to root the tree.

This is not universally accepted, though, and the asprete (''Romanichthys valsanicola'') has been more recently placed within the genus '' Zingel''.

Two clades are within the genus, a Eurasian one and a North American one, which separated from a common ancestor around 20.8 million years ago (Mya) in the Miocene, when the North Atlantic Land Bridge connecting Europe to eastern North America subsided. The Eurasian clade then speciated from 13.8 Mya, while the two North American species speciated around 5.4 Mya.

The relatively old divergences given for North American and Eurasian ''Sander'' are supported by the discovery of a fossil ''Sander'' from the middle Miocene (16.3 to 13.6 mya)-aged Wood Mountain Formation of Canada. Prior to this discovery, it was suggested that ''Sander'' may have potentially been a much more recent immigrant to North America, potentially as young as the Pliocene. In Eurasia, fossils of the extant ''S. lucioperca'' and the extinct '' S. svetovidovi'' are known from the Late Miocene and early Pliocene of Ukraine. These fossils also suggest a coexistence between ''Sander'' and their close relative, the now-extinct '' Leobergia''. It has been theorized that ''Sander'' was more tolerant than ''Leobergia'' to the global cooling that occurred during the Pliocene, leading to the extinction of the latter.

References

*

External links

FishBase list of ''Sander'' species

UN: True Name for Pike Perch

{{DEFAULTSORT:Sander (Genus)
Luciopercinae
Freshwater fish genera
Freshwater fish of Europe