Mexico is a biodiverse country in several taxa as reptiles, that include several species of freshwater and marine turtles. Eventhough most of this group species are under protection, Tabasco State has nine native freshwater turtles, like <span name="style_italic">Kinosternon leucostomum, Trachemys scripta </span>and<span name="style_italic"> Staurotypus triporcatus</span> that are very important in traditional dishes. This has resulted in a critical level of their populations, together with little biological knowledge for their conservation. Therefore, this study was dedicated to turtle cytogenetics. The study was conducted using the conventional methods for cytogenetics. The results showed the modal diploid and haploid number for <span name="style_italic">K. leucostomum</span> of 2n=56 (2n=56+3 microchromosomes “B”) and 1n=28 chromosomes in mitosis and meiosis, respectively. In <span name="style_italic">T. scripta</span> 2n=50 chromosomes (2n=50+2 microchromosomes “B”) and 1n=25 chromosomes were also characterized. Whereas in <span name="style_italic">S. triporcatus</span> we only report the 2=54 chromosomes (2n=54+2 microchromosomes “B”). The karyological formula for <span name="style_italic">K. leucostomum</span> was integrated by 12 metacentric-submetacentric chromosomes “msm”/”A”+22 subtelocentrictelocentric chromosomes “stt”/”B”+22 telocentric chromosomes “T”/”C” with fundamental number (FN) of 90 chromosome arms. While <span name="style_italic">T. scripta</span> karyotype was integrated by 32 “msm/”A”+10 “stt”/”B”+8”T/”C” chromosomes, with FN of 92 arms. <span name="style_italic">S. triporcatus</span> karyotype formula was built up by 20 chromosomes “msm”/”A”+34 chromosomes “T”/”C” with FN of 74. The variation in chromosome classification, the fundamental number and the presence of supernumerary microchromosomes “B” in the studied species, were evidence of a particular chromosome cytotypes in Tabasco. We considered that the presence of microchromosomes “B” probably has different origins, and they may be very important as a pattern for the formation or separation of new species. This study also showed the absence of heterologous chromosomes between the females and males karyotypes from the studied species. Rev. Biol. Trop. 62 (2): 671-688. Epub 2014 June 01. karyotype formula was built up by 20 chromosomes “msm”/”A”+34 chromosomes “T”/”C” with FN of 74. The variation in chromosome classification, the fundamental number and the presence of supernumerary microchromosomes “B” in the studied species, were evidence of a particular chromosome cytotypes in Tabasco. We considered that the presence of microchromosomes “B” probably has different origins, and they may be very important as a pattern for the formation or separation of new species. This study also showed the absence of heterologous chromosomes between the females and males karyotypes from the studied species. Rev. Biol. Trop. 62 (2): 671-688. Epub 2014 June 01.

citogenética cariotipo; microcromosomas B; tortugas; Tabasco