Abstract
Cytogenetic studies were performed on five closely related microteiid lizards (Gymnophthalmini), three Calyptommatus species and Psilophthalmus paeminosus from the sand dunes of the middle Sao Francisco river in the semiarid caatinga of the Brazilian state of Bahia and Tretioscincus oriximinensis from the Brazilian Amazon region. The diploid chromosome number in Calyptommatus species was 2n = 58 in females and 2n = 57 in males due to a multiple X1X1X2X2:X1X2Y sex chromosomes system, while P. paeminosus was 2n = 44 (20M+24m): where M = macrochromosomes and m = microchromosomes) and T. oriximinensis 2n = 42 (18M+24m). A single pair of silver staining nucleolar organizing regions (Ag-NORs) characterizes all five species. Incorporation of 5-BrdU (Bromodeoxyuridine) followed by replication R-banding (RBG) karyotyping allowed the identification of the larger pairs of chromosomes through longitudinal bands and the late replicating regions. Our data reinforce the remarkable chromosomal variability that has been found in the Gymnophthalmidae and the importance of using differential staining for comparative cytogenetics within this group of lizards. Chromosomal evolution in Gymnophthalmini seems to have included chromosomal fission and fusion, pericentric inversions and variation in the amount and localization of constitutive heterochromatin and the Ag-NOR pattern. Different mechanisms of sex determination also evolved independently in this radiation.
Highlights
The family Gymnophthalmidae is composed of a morphologically and ecologically diverse group of small to medium-sized lizards referred to as microteiids
Materials and Methods Cytogenetic analyses were performed on the following specimens: seven male and one female Calyptommatus leiolepis (Figure 1); two female and two male C. nicterus; three male C. sinebrachiatus; five males, two females and five embryos of Tretioscincus oriximinensis; and five male, one female and two immature Psilophthalmus paeminosus
Female specimens of Calyptommatus leiolepis present a karyotype comprised of a metacentric pair 1, distinctly larger than the remaining chromosomes, 26 pairs of acrocentric autosomes decreasing gradually in size and a small pair of submetacentrics
Summary
The family Gymnophthalmidae is composed of a morphologically and ecologically diverse group of small to medium-sized lizards referred to as microteiids. At present 35 genera are known containing about 180 species, the Gymnophthalmidae is still far from taxonomically well-described at the suprageneric, generic or specific level (Pellegrino et al, 2001; Castoe et al, 2004) and only a few species have been karyotyped because the members of this family are rare, small and difficult to collect. Admitted relationships (Rodrigues, 1995, 1996) for this radiation are (Tretioscincus (Micrablepharus (Gymnophthalmus (Procellosaurinus, Vanzosaura) (Psilophthalmus (Nothobachia, Calyptommatus))))), the habitats of theses species being as follows: Tretioscincus occurs in the Brazilian Amazon; Micrablepharus and Vanzosaura in open areas of Brazilian cerrado (woodland savannas) and caatinga (semi-arid bush) and the Chaco (tropical and subtropical dry broadleaf forests); Gymnophthalmus in Central America, some Caribbean islands and on the northern bank of the Amazon river in the Brazilian Amazon; and Calyptommatus, Nothobachia, Yonenaga-Yassuda et al
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