Somatic and Germinal Chromosomes of a Live-Fish,Heteropneustes Fossilis(Bloch)

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Abstract
The chromosome number in 223 metaphases of the kidney of colchicine pretreated 6 males and 7 females of Heteropneustes fossilis has been determined. The diploid number of 56 chromosomes was found in 90.67% metaphases in males and 81.75% in females. Some metaphases were aneuploid and polyploid in constitution in both the sexes. The karyotypes in both the sexes consisted of 7 pairs of metacentric, 13 pairs of submetacentric and 8 pairs of acrocentric chromosomes. The longest pair of metacentric chromosomes has been demarcated as the ‘marker pair’ while the rest were gradually seriated. The mean length in micra of the haploid set of 28 chromosomes ranged between 4.15 and 1.52 in male, 3.99 and 1.42 in female. On the basis of the centromeric index the chromosome formula has been determined to be n=7m + 13sm + 8st. The spermatogonial metaphase complements contained mostly 56 chromosomes. Very few were tetraploid and aneuploid in constitution. Metaphase I contained 28 stumpy rod-like bivalents. The sex chromosomes were not demarcable in the metaphase complement of kidney and the testes. Discussions have been made with regard to the difference in the chromosome sizes in two sexes, the mechanism of the evolution of chromosome number and the findings of other authors with the present one.

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