Chromosomal studies on sphaerodactyl lizards of genera <i>Gonatodes</i> and <i>Coleodactylus </i>(Squamata, Gekkonidae) using differential staining and fragile sites analyses

Abstract

The karyotypes of three species of sphaerodactyl gekkonid lizards are described after conventional and differential staining. Karyotypes of Gonatodeshumeralis and G. hasemani are formed by a gradual series of 32 acrocentric chromosomes, similar to those already published for other species of the genus. G. humeralis shows multiple Ag-NORs with intra-individual variability, and positive C-bands located at centromeric and telomeric regions of several chromosome pairs. Coleodactylus amazonicus, the first non-Gonatodes sphaerodactyl studied so far karyologically, exhibits 36 acrocentric/subtelocentric chromosomes and a single pair of Ag- NORs. Fragile sites were detected on two medium-sized chromosome pairs in the karyotype of G. humeralis, most of them obtained in BrdU-treated culture preparations. These sites may represent a putative fission/fusion spot involved in the differentiation of G. humeralis-like 2n = 32 and C. amazonicus-like 2n = 36 karyotypes. Our results, especially on the location of Ag-NORs and the description of fragile sites, are relevant in improving our knowledge about the events of chromosome evolution in this extremely variable and poorly known group of lizards.

Cytogenetic Studies on Gonatodes (Reptilia, Squamata, Sphaerodactylidae)

“…These have also been detected in 2 specimens of G. humeralis , in which 1-8 NORs were present at the long arm telomeric regions of several telocentric chromosomes [dos Santos et al, 2003].…”

“…The direct induction of G-and Rbands in the chromosomes of reptiles and other poikilothermic vertebrates, either by enzymatic treatment or by heating in specific buffer solutions, is not possible or yields unsatisfactory results [for reviews, see Schmid and Guttenbach, 1988;Schmid et al, 2010]. Although the induction of R-bands with the 5-bromodeoxyuridine (BrdU) replication banding technique is possible in the chromosomes of Gonatodes [dos Santos et al, 2003] and other reptiles, the small size of most reptile chromosomes and the low number of induced R-bands inhibit the identification of the corresponding homeologous chromosome regions. On the other hand, chromosome-specific DNA probes have not yet been generated for Gonatodes or other sphaerodactylids.…”

A Review of Sex Determining Mechanisms in Geckos (Gekkota: Squamata)

“…Only 2 of these species, G. humeralis and G. hasemani have karyotypes from both sexes [dos Santos et al, 2003] and, as mentioned above, only 1 species, Gonatodes ceciliae , possessed heteromorphic sex chromosomes. Evidence for heteromorphic sex chromosomes comes from 2 male G. ceciliae , captured from the same locality in Trinidad [McBee et al, 1987].…”

“…The 2 remaining species in Sphaerodactylidae that have been karyotyped involved just single individuals, a female Coleodactylus amazonicus, and a male Pristurus carteri , no heteromorphic chromosome pairs were reported for either species [Branch, 1980;dos Santos et al, 2003]. …”

Estudos evolutivos em espécies de lacertílios brasileiros da família Teiidae (Squamata), com base em dados citogenéticos e moleculares

“…Dessa forma, somente com os avanços na técnica de cultura de fibroblastos, padrões longitudinais de bandamento foram obtidos pela incorporação da 5'-Bromodeoxiuridina (5-BrdU), uma substância análoga à timidina, que se incorpora nas regiões ricas em AT. A descrição do padrão de bandas R em lacertílios obtidos por incorporação de 5-BrdU e 5-FudR (5´-Fluordeoxiuridina) em cultura de fibroblastos é rara na literatura, existindo dados para algumas espécies de geconídeos (PELLEGRINO et al, 1995(PELLEGRINO et al, , 1997VOLOBOUEV et al, 1993;VOLOBOUEV & INEICH, 1994;SANTOS et al 2003), tropidurídeos (KASAHARA et al, 1987a(KASAHARA et al, ,b, 1996YONENAGA-YASSUDA et al, 1988;RODRIGUES et al, 1989;PELLEGRINO et al, 1994;BERTOLOTTO et al, 1996), policrotídeos (PELLEGRINO et al, 1999a;, microteídeos , PELLEGRINO et al, 1999b e teídeos (SANTOS et al, 2007).…”