The Effects of Estrogenic Endocrine Disruptors on the Osmoregulatory Functions in Euryhaline Fish
Thesis or dissertation
University of Exeter
Submitted by Noura Jalal Al-Jandal, to the University of Exeter as a thesis for the degree of Doctor of Philosophy in Biological Sciences in January 2011 This thesis is available for library use on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement I certify that all material in this thesis which is not my own work has been identified and that no material previously submitted and approved for the award to a degree by this or any other University.
Reason for embargo
To enable publication of the thesis
ABSTRACT Osmoregulation is an essential process to maintain water and ionic balance and when euryhaline fish move between freshwater and seawater environments as part of their life cycle this presents additional osmoregulatory challenges. Migrating fish can be exposed in both environments to pollutants such as endocrine disrupting chemicals (EDCs) that include natural hormones (e.g. 17β-estradiol; E2), synthetic hormones (e.g. 17α-ethinylestradiol; EE2), and industrial chemicals (e.g. nonylphenol). The focus of this thesis was to study the effects of different categories of EDCs on the osmoregulatory functions of euryhaline fish such as three-spined sticklebacks (Gasterosteus aculeatus) and rainbow trout (Oncorhynchus mykiss). Osmoregulatory variables (such as osmolality, water and ionic content) were compared in plasma and tissues (white muscle and carcass) of rainbow trout. This validated the use of specific tissue parameters as a surrogate of plasma responses to various osmoregulatory challenges. Waterborne exposure to 17α-ethinylestradiol revealed differential sensitivity of vitellogenesis in the three-spined sticklebacks (no induction) and rainbow trout, but had a significant effect on calcium homeostasis in both species. Intraperitoneal implants of 17β-estradiol reduced CaCO3 production and apparent water absorption in the intestine and increased in tissue calcium stores of seawater-acclimated trout, but fish were able to compensate and showed no overall osmoregulatory disturbance. Waterborne exposure to nonylphenol in freshwater trout was also investigated, but no effects on osmoregulation were found up to 2 ng/l. Overall, estrogens can affect osmoregulation differentially in euryhaline fish species, and sometimes at EDC levels lower than the threshold for reproductive effects (i.e. vitellogenin induction).
Kuwait Institute for Scientific Research (KISR)
Al-Jandal and Wilson, 2011
Al-Jandal et al., 2011
PhD in Biological Sciences