 The distribution of NADPH-diaphorase activity was studied in the cichlid fish Tilapia mariae, during the first developmental stages by means of the tetrazolium salt technique.     ///    Developmental pattern of NADPH-diaphorase activity in the peripheral nervous system of the cichlid fish Tilapia mariae..     ///    The present results indicate an early activity of NADPH-diaphorase during the development of the peripheral nervous system of Tilapia and reveal a gradual maturation of NADPH-diaphorase positive structures.. 