Gamete viability as an indicator of reproductive endocrine disruption in fish

Xenobiotic pollutants may disrupt reproductive endocrine function by acting at the hypothalamus, pituitary, gonad or liver. Disruption at any of these sites may result in either changes in the rate of gonadal development or i n the viability of the gametes. Production of high quality gametes is depen dent upon the correct hormonal milieu throughout their development, and any disruption of hormonal balance may result in abnormal sperm or eggs. Such effects may be apparent at levels of pollutant lower than that which causes arrest of gametogenesis or decreased gonadosomatic index. In this paper th e use of sperm motility, morphology and fertilising ability in males, and e gg numbers, size and hatching success in females as monitors of endocrine d isruption will be discussed. Data are presented to show that exposure of ad ult zebra danios (Danio rerio) to 5 ng l(-1) ethynylestradiol leads to arre st in development of the eggs produced at the early blastula stage and indu ces vitellogenesis in exposed males. (C) 1999 Elsevier Science B.V. All rig hts reserved.