Main neuro-endocrine, endocrine and paracrine regulations of fish reproduction, and vulnerability to xenobiotics

The reproductive function of fish, which is very sensitive to the variations of environmental factors, appears also to be particularly vulnerable to the presence of xenobiotics in the aquatic medium. Many physiological processes can be impaired, from sexual differentiation to female and male gametogenesis, due to disruptions among complex neuro-endrocrine, endocrine or paracrine regulations. This paper describes the main regulation steps that are known or can be suspected to be disrupted by xenobiotics and gives some examples. The large interspecific diversity of reproductive strategies and the complexity of underlying mechanisms are particularly highlighted to draw attention to possible confusions between real endocrine disruptions and natural physiological variations.