Induction of gonadal sex reversal in adult gonochorist teleost by chemical treatment: an examination of the changing paradigm

Abstract

Abstract Background Gonochorist teleosts are teleosts in which individuals develop either as males or as females, and are sexually stable thereafter throughout ontogeny. However, there is a labile period, defined as the time period prior to hatching through juvenile stage before sexual maturation (adulthood), during which gonadal sex differentiation can be influenced by environmental conditions, including exogenous chemical treatments. Usually, during this period, depending on the nature of chemical treatment, gonadal sex can be reversed from one phenotypic sex to another. A number of chemicals, ranging especially from sex steroids (natural and synthetic) to the more recent one, aromatase inhibitors, have been employed for the purpose of sex reversal in different gonochorist teleost species during the labile period. Thus, the labile period requirement for treatment application before adulthood in order to achieve gonadal sex reversal in gonochorist teleost is well founded. Interestingly, however, some degree of gonadal bipotentiality has recently been reported with mixed findings in adults of certain gonochorist teleost species upon treatment with exogenous chemicals, especially aromatase inhibitors. Consequently, it is now widely thought that gonochorist teleost species are amenable to chemical-induced gonadal sex reversal after sexual maturity. Method Here, all studies on chemical-induced gonadal sex reversal in adult gonochorist teleosts were reviewed. Results Data strongly suggest that there are certain gonochorist teleost species in which adults may not be amenable to gonadal sex reversal through 17β-estradiol depletion by aromatase inhibitors and that the generalization of chemical-induced gonadal sex reversal remains to be experimentally determined in adult gonochorist teleost. Conclusion It was concluded that further studies are required for clarification, considering, among others, that population-level effect models of these chemicals on wild fish populations are based on the understanding that environmental sex reversal occurs only during development and not after sexual maturity.