The origin and migration of primordial germ cells in the mouse. Results from long-term field investigations of grayling in a lake of Switzerland strongly suggest that the sex ratio is correlated with the average temperature that the juvenile fish experienced during their first summer and that temperature change was involved in the decline of the population [ ].
In contrast to the high conservation of most developmental pathways across species from Drosophila to man, a stunning variety of mechanisms of sex determination exist within the animal kingdom. Lutnesky, M.
Although how the ambient temperature transduces signals to the undifferentiated gonads remains to be elucidated, the genes downstream in the sex differentiation pathway are shared between sex-determining mechanisms. In contrast, in the Nile tilapia in which the sex ratio is genetically determined with strong temperature effects, dmrt1 expression presented a rapid up-regulation pattern during the critical period of sex differentiation at high temperature in both the XY and XX male population [ 5 ], which implies that in this species dmrt1 is involved in testicular differentiation and high-temperature induced sex reversal.
Animals utilizing TSD are susceptible to increases in temperature, as well as exposure to chemicals, such as synthetic estrogens. Transcription factor, upregulator of Sox9, DM domain gene; and testis-determining gene.
View at: Google Scholar M. J Morphol 3 — Proc Biol Sci —
Fitness-compromised YY individuals will therefore not arise in the next generation, and both mechanisms might be simultaneously maintained without significant risk. Veyrunes, F. Y TIR sex-reversed mouse ovary.
Animals with both male and female phenotypic characteristics, often distributed bilaterally. Genesis 28 , — However, mechanisms of sex determination based on antagonistic signaling could be highly labile in evolutionary terms, and might easily be regulated in diverse ways.