Monster Seminar Jam - Reproductive impairment and endocrine disruption in an estuarine fish population exposed to seasonal hypoxia
Dr. Peter Thomas, Research Assistant Professor, Marine Science Institute, Department of Marine Science and Section of Intergrative Biology , Universit
The long term effects of the recent dramatic increase worldwide in the incidence of coastal hypoxia on marine ecosystems are unknown. Here we show that chronic environmental exposure of Atlantic croaker to hypoxia in a Florida estuary in 2003 caused marked suppression of ovarian and testicular growth. The suppression of ovarian growth and egg development in female croaker was associated with lower levels of circulating estrogens, hepatic estrogen receptor mRNA expression and plasma vitellogenin, indicating an impairment of estrogen signaling after hypoxia exposure. Similarly, inhibition of testicular growth and sperm production in males from the hypoxic sites was accompanied by lower plasma androgen levels. Laboratory hypoxia studies showed that the endocrine disruption was associated with impairment of reproductive neuroendocrine function and decreases in hypothalamic serotonin content and the activity of the serotonin biosynthetic enzyme, tryptophan hydroxylase. Pharmacological restoration of hypothalamic serotonin levels also restored neuroendocrine function, indicating that the stimulatory serotinergic neuroendocrine pathway is a major site of hypoxia-induced inhibition. Down-regulation of reproductive activity through inhibition of tryptophan hydroxylase activity could have evolved as an adaptive mechanism to survive periodic hypoxia, but in view of the recent increased incidence of coastal hypoxia could potentially affect fish population abundance and threaten valuable fishery resources.
Date and Time:
November 15, 2007,
10:30 am - 12:30 pm