Morphological and mtDNA sequence studies on three crucian carps (Carassius: Cyprinidae) including a new stock from the Ob River system, Kazakhstan.

Three morphologically and genetically distinct forms of the genus Carassius were collected from the Ob River system, Kazakhstan, Central Asia; Carassius carassius, Carassius gibelio gibelio and an unknown stock tentatively referred to as Carassius gibelio sub-species M. The last mentioned had 33-41 gill rakers, being intermediate between the other two forms (23-27 in C. carassius and 44-49 in C. g. gibelio), and five scales in the upper transverse series, less than in the others. It also had a relatively larger erythrocyte suggesting triploidy and an mtDNA haplotype distinct from all other known crucian carps. Comparative mtDNA phylogenetic analysis suggested that C. gibelio gibelio in the Ob River system was introduced from China and the Amur River, the same possibly being true for European C. gibelio gibelio based on published haplotypes. C. gibelio sub-species M is thought to be more widely distributed in central Asia, probably extending as far west as European Russia.