Karyotypes of the lenok genus Brachymystax from the Amur River basin ? AgNORs are diff erent between sharp-snouted and blunt-snouted lenoks

Abstract

Two sympatric forms of the Siberian lenok genus Brachymystax, sharp-snouted lenok (B. lenok, SS) and blunt-snouted lenok (B. tumensis is applied currently, BS), from the Amur River basin shared similar karyotype showing 2n = 90 and the formula of 8M+1SM+1SMST+9ST+27A, with NF = 110. However, AgNORs were located on one each pair of acrocentric and subtelocentric chromosomes in the SS lenok, and only one pair of subtelocentric chromosomes in the BS lenok. The observed karyotypic difference strongly supported these two forms to be different species. Variations of previously published lenok karyotypes also were discussed.