Supernumerary chromosome variation, heteromorphic sex chromosomes and banding patterns in microteiid lizards of the genus Micrablepharus (Squamata, Gymnophthalmidae)

Cytogenetic investigations using differential staining (C-, replication R-banding and Ag-NOR staining) were performed in the two known species of the microteiid lizards of the genus Micrablepharus: M. maximiliani and M. atticolus. M. atticolus showed diploid number variation (2n = 50, 51, 52, 53) due to a system of supernumerary chromosomes which presented late replication patterns and differences in morphology (metacentric and submetacentric) and size. M. maximiliani revealed three different cytotypes (I, II and III) in a sample of only three animals. Two of them (cytotypes I and III) had 2n = 50, and the other (cytotype II) showed 2n = 51, with one B chromosome, all of them with difference in the number of autosome arms. A comparative analysis of the basic karyotype of M. atticolus (2n = 50) and the three cytotypes of M. maximiliani revealed differences in the number of biarmed and uniarmed chromosomes, probably due to several pericentric inversions. The genus Micrablepharus exhibited a remarkable variability in number and location of Ag-NORs including single and multiple NOR-bearing chromosome pairs. Variation of C-banding patterns was found in M. maximiliani and M. atticolus and that seems to be related to a species-specific trait. Sex determination of the XX:XY type was observed for both species.