title: Widespread endocrine disruption and reproductive impairment in an estuarine fish population exposed to seasonal hypoxia.
abstract: The long-term effects on marine fish populations of the recent increase worldwide in the incidence of coastal hypoxia are unknown. Here we show that chronic environmental exposure of Atlantic croaker (Micropogonias undulatus) to hypoxia in a Florida estuary caused marked suppression of ovarian and testicular growth which was accompanied by endocrine disruption. Laboratory hypoxia studies showed that the endocrine disruption was associated with impairment of reproductive neuroendocrine function and decreases in hypothalamic serotonin (5-HT) content and the activity of the 5-HT biosynthetic enzyme, tryptophan hydroxylase. Pharmacological restoration of hypothalamic 5-HT levels also restored neuroendocrine function, indicating that the stimulatory serotonergic neuroendocrine pathway is a major site of hypoxia-induced inhibition. Inhibition of tryptophan hydroxylase activity to downregulate reproductive activity could have evolved as an adaptive mechanism to survive periodic hypoxia, but in view of the recent increased incidence of coastal hypoxia could become maladaptive and potentially affect fish population abundance and threaten valuable fishery resources.
authors.affiliation: Marine Science Institute, University of Texas at Austin, 750 Channel View Drive, Port Aransas, TX 78373, USA. thomas@utmsi.utexas.edu
authors.forename: Peter
authors.initials: P
authors.lastname: Thomas
authors.forename: Md Saydur
authors.initials: MS
authors.lastname: Rahman
authors.forename: Izhar A
authors.initials: IA
authors.lastname: Khan
authors.forename: James A
authors.initials: JA
authors.lastname: Kummer
mesh_terms: D000818:Animals; D017753:Ecosystem; D005260:Female; D007987:Gonadotropin-Releasing Hormone; D006897:Hydroxyindoleacetic Acid; D000860:Hypoxia; D007986:Luteinizing Hormone; D008297:Male; D010053:Ovary / Q000254:growth & development; D010060:Ovulation; D010473:Perciformes / Q000502:physiology*; D012333:RNA, Messenger; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D012701:Serotonin / Q000378:metabolism; D013091:Spermatogenesis; D013737:Testis / Q000254:growth & development; D014365:Tryptophan Hydroxylase; D014867:Water / Q000737:chemistry
chemical_list: D012333:RNA, Messenger; D014867:Water; D012701:Serotonin; D007987:Gonadotropin-Releasing Hormone; D006897:Hydroxyindoleacetic Acid; D007986:Luteinizing Hormone; D014365:Tryptophan Hydroxylase