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In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Environmental sex determination ESD has been detected in a range of vertebrate reptile and fish species. Because several eel species are at risk of extinction, assessing sex at the earliest stage is a crucial management issue. Based on preliminary results of RNA sequencing, we targeted genes susceptible to be differentially expressed between ovaries and testis at different stages of development.
Using qPCR, we detected testis-specific expressions of dmrt1 , amh , gsdf and pre - miR and ovary-specific expressions were obtained for zar1 , zp3 and foxn5. We showed that gene expressions in the gonad of intersexual eels were quite similar to those of males, supporting the idea that intersexual eels represent a transitional stage towards testicular differentiation. To assess whether these genes would be effective early molecular markers, we sampled juvenile eels in two locations with highly skewed sex ratios.
The combined expression of six of these genes allowed the discrimination of groups according to their potential future sex and thus this appears to be a useful tool to estimate sex ratios of undifferentiated juvenile eels. To date, environmental sex determination ESD has been detected in many vertebrates including turtles, sphenodons, crocodiles, lizards and fish species 1. Protecting endangered species with ESD from decline should necessarily take into account this particularity that ultimately influences adult sex ratio 2.
For instance, it has recently been emphasized that turtle conservation projects might benefit from the knowledge acquired on ESD to efficiently manage populations shading clutches was effective in reducing nest temperature, producing more males without compromising the fitness or hatching success 3. Early assessment of the sex of future spawners is of prime importance in order to consider the whole population dynamic 4 , 5 , build reliable stock-recruitment models 6 , 7 and potentially help producing the rarer sex 3.
