Date:7/29/2008

far less widespread than currently believed, suggesting that TSD is clearly the exception in fish sex-determination. Thus, the scientists suggest that the evolution of sex-determining mechanisms in lower vertebrates, as is currently understood, needs to be revised. Further, species with TSD exhibit only one general change in sex ratio in response to temperature increase (leading to many males and few females). In many species, females determine the number of offspring for the next generation and so the viability of some fish populations with TSD can be compromised through alterations in their sex ratios due to temperature fluctuations of the magnitude predicted by climate change.

The researchers identify two key questions for future research. Firstly, whether the predicted effects can be observed in sensitive, natural populations there are indications that this could be the case in some populations of South American silversides. Secondly, while it is already known that high temperatures inhibit the synthesis of estrogens, which are essential for female sex differentiation in fish and reptiles, more work needs to be done into the molecular mechanism linking environmental temperature and estrogen synthesis.

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Contact: Francesc Piferrer piferrer@icm.csic.es Public Library of Science Source:Eurekalert

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