Chromosomal distribution of constitutive heterochromatin in eight species of mahseers (Family: Cyprinidae) from India

Abstract

The chromosomal distributions of constitutive heterochromatin were analyzed in 8 species of mahseer, namely, Tor chelynoides (McClelland), T. khudree (Sykes), T. mosal mahanadicus (David), T. mussullah (Sykes), T. putitora (Hamilton), T. progeneius (McClelland), T. tor (Hamilton) and Neolissochilus hexagonolepis (McClelland) using C-banding technique. The constitutive heterochromatin bands were observed on several pairs of chromosomes with maximum numbers in T. progeneius (11 pairs), followed by T. putitora (7 pairs), T. mosal mahanadicus (4), T. khudree (3), T. mussullah (3), N. hexagonolepis (3), T. chelynoides (3) and T. tor (2). In all species, the C-bands were observed mainly on p arm with few on centromeric region of chromosomes. This seems to be the characteristic feature for characterization of these species. The presence of similar chromosome numbers (2n=100) with diverse karyotypes in the mahseer species suggests evolution among the species through pericentric inversions and/or heterochromatin processes. The number and location of the heterochromatic bands were found species-specific and thus useful for the cytotaxonomy of these species. The findings of the present study can also help to understand the evolutionary relationships among the mahseer species .