1 URA 1137, 2 place Jussieu, 75251 Paris cedex 05, France
2 Institut Jacques Monod, 2 place Jussieu, 75251 Paris Cedex 05, France
KEYWORDS: Sex determination, TSD, GSD, Sex chromosome, genetic
Sex determination in sauropsids is classically referred to as mutually exclusivegenotypic sex determination (GSD) or temperature-dependent sex determination(TSD). The European freshwater turtle, Emys orbicularis, exhibits TSD, anincubation temperature below 28°C being masculinizing, and one above 29.5°C beingfeminizing. Between 28°C and 29.5°C, both sexes are produced. However, two majorarguments suggest the influence of a strong genetic component in sexdetermination for this spetion for this species. First, the influence of a genetic component insex determination has been demonstrated for artificially incubation at 28.5°C.Second, the expression of H-Y antigen analyzed in artificial incubated embryosand adults of natural populations demonstrates a major influence of a geneticcomponent superimposed on the temperature effect. However, neither of thesearguments proves definitively the influence of a genetic component in sexdetermination. Therefore, a polymorphic marker of the genetic component has beensearched using microsatellites. An original strategy has been used to detectrapidly such a marker. Approximately 30 markers have been tested and one shows alarge difference of frequency among male and female adults of three testedpopulations from central France. Further analyses have shown that themicrosatellite is a tandem repeat of GGCT with 7 alleles. The distribution ofalleles is significantly different between males and females. This couldcorrespond to a polymorphic marker shared by sex chromosomes of Emys orbicularis,a species with both TSD and GSD.h TSD and GSD.