Chromosomal banding patterns in the eyelid-less microteiid lizard radiation: The X1X1X2X2:X1X2Y sex chromosome system in Calyptommatus and the karyotypes of Psilophthalmus and Tretioscincus (Squamata, Gymnophthalmidae)

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 São 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 X 1 X 1 X 2 X 2 :X 1 X 2 Y 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.

Lizards as Model Organisms of Sex Chromosome Evolution: What We Really Know from a Systematic Distribution of Available Data?

“…In particular, reports of TSD in C. chamaeleon is anecdotical [ 145 ], and recent studies on this species and on the congeneric C. calyptratus evidenced the presence of homomorphic XY sex chromosomes [ 13 , 99 ]. Concerning p. pityusensis and V. salvator , qPCR studies by Rovatsos et al [ 113 , 146 , 147 , 148 ] evidenced a ZW sex chromosome system, while TDS in Elgaria multicarinata was not supported by incubation experiments by Reference [ 147 ]. Furthermore, the probable lack of TSD in Lacertidae has been discussed by Rovatsos et al [ 149 ], who found evidence of a conserved ZW system in the family.…”

“…In a significant number of lizard species (see below), the main described pathways of sex chromosome diversification ( Figure 1 A,B) can also be modified by further chromosome rearrangements leading to the formation of multiple sex chromosome systems (X 1 X 1 X 2 X 2 /X 1 X2 Y and Z 1 Z 1 Z 2 Z 2 /Z 1 Z 2 W) ( Figure 1 C). Such configurations are originated from a Y/W-autosome fusion, producing an odd diploid chromosome complement in the heterogametic sex (e.g., References [ 10 , 75 , 113 , 114 ]).…”

Sex Chromosome Evolution in Lizards: Independent Origins and Rapid Transitions

“…[Gorman and Aitkins, 1968], AMO: Anolis monesis [Gorman and Stamm, 1975], BDU: Bassiana duperreyi [Shine et al, 2002], BTR: Bipes tridactylus [Cole and Gans, 1987], CEN: Claireascincus entrecasteauxii [Hutchinson and Donnellan, 1992], CLE: Calyptommatus leiolepis [Yonenaga-Yassuda et al, 2005], CLI: Cnemidophorus littoralis [Peccinini-Seale et al, 2004], CTI: Cnemidophorus tigris [Cole et al, 1969], DIN: Delma inornata [King, 1990], DNO: Dibamus novaeguineae [Cole and Gans, 1997], GCE: Gonatodes ceciliae [McBee et al, 1987], GGE: Gekko gecko [Solleder and Schmid, 1984], GHO: Gekko hokouensis [Kawai et al, 2009], GPL: Gymnophthalmus pleei [Cole et al, 1990], GPU: Gehyra purpurascens [Moritz, 1984], LBU: Lialis burtonis [Gorman and Gress, 1970], LVI: Lacerta vivipera [Odierna et al, 2001], MAL: Micrablepharus allicolus [Yonenaga-Yassuda and Rodrigues, 1999], PLA: Phyllodactylus lanei [King, 1981], PSI: Podarchis sicula [Odierna et al, 1993], PVI: Pogona vitticeps [Ezaz et al, 2005], PVL: Phrynocephalus vlangalii [Zeng et al, 1997], SCZ: Saproscincus czechurai [Donnellan, 1991], SLA: Scincella lateralis [Wright, 1973], SLU: Sceloporus lundelli [Cole, 1970], SMA: Sceloporus maculosus [Cole, 1971], VAC: Varanus acanthurus [King et al, 1982].…”

Differentiation of sex chromosomes and karyotypic evolution in the eye-lid geckos (Squamata: Gekkota: Eublepharidae), a group with different modes of sex determination

“…This sex chromosome system evolved independently within squamate reptiles several times. It occurs in three species of the gymnophtalmid genus Calyptommatus, several species of Iguanidae sensu lato and in the skink Scincella lateralis, where closely related species or populations possess the simple XY system (Bertolotto et al 2001;Yonenaga-Yassuda et al 2005; recently reviewed in Ezaz et al 2009). It was also identified in the gekkotan lizard Lialis burtonis (Gorman and Gress 1970), where the related genus (Delma) from the same family (Pygopodidae) also posesses an XY system (King 1990).…”