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 variation s of environmental factors, appears also to be particularly vulnerable to t he presence of xenobiotics in the aquatic medium. Many physiological proces ses can be impaired, from sexual differentiation to female and male gametog enesis, due to disruptions among complex neuro-endrocrine, endocrine or par acrine regulations. This paper describes the main regulation steps that are known or can be suspected to be disrupted by xenobiotics and gives some ex amples. The large interspecific diversity of reproductive strategies and th e complexity of underlying mechanisms are particularly highlighted to draw attention to possible confusions between real endocrine disruptions and nat ural physiological variations.