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Evolution of karyotypes and sex determination in the turtle family Geoemydidae
Clemente, Lorenzo ; Rovatsos, Michail (advisor) ; Montiel Jimenez, Eugenia Elisabet (referee) ; Castiglia, Riccardo (referee)
(IN ENGLISH) The majority of studied turtles show temperature-dependent sex determination, but genotypic sex determination (i.e. presence of sex chromosomes) was identified sporadically. This thesis aims to investigate and expand our knowledge on the evolution of the karyotype and the sex determination in turtles, particularly focusing on the family Geoemydidae, a group of turtles with previously documented variability in sex determination systems. The presence of sex chromosomes was explored by a combination of conventional and molecular cytogenetic techniques for the analysis of karyotypes, distribution of constitutive heterochromatin (C-banding) and repetitive elements and comparative genome hybridization (FISH, CGH). In total, 49 species of turtles from nine different families were cytogenetically examined in this study. In the family Geoemydidae, a remarkable similarity in karyotypes was identified, consisting of 2n=52 chromosomes (which is suggested to be the ancestral diploid number for all turtles) and a similar topology of rDNA loci and telomeric repeats. Sharma et al. (1975) previously reported ZZ/ZW sex chromosomes in Pangshura smithii. However, in the analysis presented in this thesis, it is suggested a possible misidentification of these sex chromosomes due to erroneous pairing of...
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