Banding patterns, heteromorphic sex chromosomes and Ag-stained NORs after pachytene stage in the meiosis of the Brazilian lizard Uroshophus vautieri (Squamata, Polychrotidae)

Mitotic and meiotic chromosomes of the Brazilian lizard Urostrophus vautier i were studied after standard and differential staining (C- and replication R-banding, and Ag-NOR). This species has a 2n=36 karyotype, characterized by 12 macrochromosomes and 24 microchromosomes, and sex chromosome heteromo rphism XX:XY with the Y corresponding to a minute microchromosome and the X to a medium-sized morphologically non-differentiated acrocentric microchro mosome. Pair 2 exhibits a conspicuous secondary constriction at the distal end of the long arm, which bears the NORs, is C-band positive, and is shown to be a late-replication region. The correspondent Ag-NORs at pair 2 were uncommonly detected beyond the pachytene stage at diakinesis and MII. Const itutive heterochromatin is located at the pericentromeric regions of macroc hromosomes and microchromosomes.