Stock-specific differences in the number and chromosome positions of the nucleolar organizer regions in arctic char <i>(Salvelinus alpinus</i><i>)</i>

Abstract

Stock-specific variation in the number and chromosome locations of the nucleolar organizer regions (NORs) was found in North American and European stocks of arctic char (<i>Salvelinus alpinus</i>) using chromomycin A<sub>3</sub> staining and silver staining. The number of NORs varied from two to eight per diploid genome. An unusual pattern of one NOR consistently present on both members of the largest submetacentric chromosome pair and additional NORs with variable locations was found. These findings suggest that NORs are being transposed to new chromosome sites in this species and this is discussed in relation to similar findings in other <i>Salvelinus </i>species and in amphibians.