Molecular Cytogenetic Characterization of theSicilian Endemic Pond Turtle Emys trinacris and theYellow-Bellied Slider Trachemys scripta scripta(Testudines, Emydidae)

Turtles, a speciose group consisting of more than 300 species, demonstrate karyotypes withdiploid chromosome numbers ranging from 2n = 26 to 2n = 68. However, cytogenetic analyses havebeen conducted only to 1/3rd of the turtle species, often limited to conventional staining methods.In order to expand our knowledge of the karyotype evolution in turtles, we examined the topology ofthe (TTAGGG)n telomeric repeats and the rDNA loci by fluorescence in situ hybridization (FISH)on the karyotypes of two emydids: the Sicilian pond turtle, Emys trinacris, and the yellow-belliedslider, Trachemys scripta scripta (family Emydidae). Furthermore, AT-rich and GC-rich chromosomeregions were detected by DAPI and CMA3 stains, respectively. The cytogenetic analysis revealed thattelomeric sequences are restricted to the terminal ends of all chromosomes and the rDNA loci arelocalized in one pair of microchromosomes in both species. The karyotype of the Sicilian endemicE. trinacris with diploid number 2n = 50, consisting of 13 pairs of macrochromosomes and 12 pairsof microchromosomes, is presented here for first time. Our comparative examination revealedsimilar cytogenetic features in Emys trinacris and the closely related E. orbicularis, as well as to otherpreviously studied emydid species, demonstrating a low rate of karyotype evolution, as chromosomalrearrangements are rather infrequent in this group of turtles.