Zebrafish sex differentiation and gonad development: A review on the impact of environmental factors.

Zebrafish (Danio rerio) is extensively used in research; however the mechanisms that control this species sex determination are still poorly understood. In the latest decades, it has been established that zebrafish sex is determined by genetic factors on a polygenic basis, as various candidate genes with sex dimorphic expression, as well sex-linked loci have been identified in different zebrafish strains. However, it has been evidenced that sex determination in this species is also influenced by environmental factors. For instance, temperature can have a crucial role in zebrafish sex determination. Likewise, the exposure to endocrine disrupting chemicals (EDCs), the most studied zebrafish sex changing factor, can strongly influence the course of sex differentiation and unbalance the sex ratio of zebrafish populations. Despite this, so far the influence of environmental factors is still less understood and only few studies have addressed this topic. Therefore, this review intends to gather current knowledge on the environmental factors involved in sex determination of zebrafish and identify important gaps in this research area. Briefly, the current understanding on zebrafish sex related genetics is also addressed.