Chromosomal polymorphisms due to supernumerary chromosomes and pericentric inversions in the eyelidless microteiid lizard Nothobachia ablephara (Squamata, Gymnophthalmidae).

Abstract

Cytogenetic studies were performed on eight specimens of the monotypic microteiid lizard Nothobachia ablephara, endemic of the sand dunes of the middle São Francisco river, in the semiarid caatinga, State of Bahia, Brazil. Chromosomes from fibroblast cultures were analysed after conventional, Ag-NOR staining, C-, and replication R- banding. A basic karyotype of 2n = 62, consisting mostly of subtelocentric and acrocentric chromosomes of decreasing size, was found in five specimens. Diploid number variation (2n = 63 and 2n = 64) occurred in two specimens due to the presence of one and two medium-sized subtelocentric supernumerary chromosomes (Bs). The Bs were not clearly distinguishable from the autosomes in Giemsa-stained metaphases and C-banding, but showed late replication after R-banding. Polymorphisms of pairs 1 and 5, observed in three different combinations, including acrocentrics, subtelocentrics, submetacentrics and metacentrics, were interpreted as the result of small pericentric inversions. Variation in the number of Ag-NORs was also reported. A chromosomal mechanism of sex determination of the XX:XY type is present in this species. Our data add more evidence to confirm the remarkable chromosomal variability that has been found in Gymnophthalmidae.