CYTOGENETIC AND DNA CONTENT IN 6 GENERA OF THE FAMILY CALLICHTHYIDAE (PISCES, SILURIFORMES)

Cytogenetic studies involving conventional Giemsa staining, C-banding analysis and silver staining of NORs were performed on nine species be longing to six genera of the family Callichthyidae. The diploid number ranged from 2n = 44 to 2n = 100, the number of chromosomal pairs with NORs ranged from 1 to 4 and constitutive heterochromatin was mainly d istributed in the centromeric and/or pericentromeric position of the c hromosomes. The DNA content of erythrocytes from six species studied r anged from 1.18 +/- 0.07 to 2.77 +/- 0.22 pg/nucleus. The extensive va riability in karyotypes and in nuclear DNA content detected are in acc ordance with the initial hypothesis that chromosome rearrangements and polyploidy have played a significant role in the evolutionary history of Callichthyidae.