Seven new karyotypes for subfamily Cercosaurinae (Squamata, Gymnophthalmidae) with a synthesis of chromosomal data

TL;DR

This study reports seven new karyotypes for lizards in the Cercosaurinae subfamily, significantly increasing chromosomal data for the group and shedding light on their chromosome evolution.

Contribution

The study triples the available cytogenetic data for two tribes in Cercosaurinae and identifies a potential sex chromosome system in one species.

Findings

Diploid numbers ranged from 2n = 32 to 2n = 58 across seven species.

A putative XX:XY sex chromosome system was identified in Bachia dorbignyi.

Constitutive heterochromatin was mostly found in centromeric or telomeric regions.

Abstract

Gymnophthalmidae is a monophyletic family of currently 297 Neotropical lizard species. Over the past 25 years, molecular studies have redefined previous morphology-based classifications, confirming the family’s monophyly and revealing three major clades plus Rachisaurinae: ((Riolaminae(Rachisaurinae(Gymnophthalminae)))(Cercosaurinae)). Despite increased taxonomic efforts, especially in the tribes Bachiini and Cercosaurini, of Cercosaurinae, cytogenetic data remain limited. Of over 200 species in these tribes, only three had published karyotypes. Here, we provide new karyotypic data for seven species of Cercosaurini using standard cytogenetic techniques (Ag-NOR, C- and RBG-banding). Diploid numbers ranged from 2n = 32 in Bachia
dorbignyi (Duméril et Bibron, 1839) to 2n = 58 in Placosoma
glabellum (Peters, 1870). Almost all species displayed karyotypes composed of macro- and microchromosomes, that varied in morphology. Ag-NORs were observed on macro- or microchromosomes in several species, with notable variability in Bachia
bresslaui (Amaral, 1935). Constitutive heterochromatin was mostly restricted to centromeric or telomeric regions. In Bachia
dorbignyi, we found a putative XX:XY system due to the presence of a dot-like microchromosome exclusively in male specimens. These results comprise the threefold amount of cytogenetic data available for Bachiini and Cercosaurini and help fill a major gap into our understanding of diversity and chromosome evolution within Gymnophthalmidae.

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