Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Michael P. Wilkie

Advisor Role

Thesis Supervisor

Abstract

The pesticide, 3-trifluoromethyl-4-nitrophenol (TFM), is widely used in the Great Lakes to control invasive sea lampreys (Petromyzon marinus) populations, but much about its sub-lethal effects remains unknown. A better understanding of its toxicity is needed to improve TFM effectiveness and to protect non-target organisms from its potential adverse effects. The objectives of this thesis were to test the following two hypotheses: (1) impairment of mitochondrial ATP production by TFM interferes with ATP-dependent ion-uptake by fish, leading to altered electrolyte balance, and (2) perturbations of gill function by TFM are exacerbated in soft, ion poor water (SW; 40 mg CaCO3 L-1). Accordingly, larval lamprey, juvenile rainbow trout (Oncorhynchus mykiss), and juvenile sturgeon (Acipenser fulvescens) were exposed to TFM concentrations toxic to larval sea lamprey for 12 h. In lamprey, the toxicity of TFM was 10-fold greater in SW compared to hard water (HW; 450 mg CaCO3 L-1). The activity and expression of Na+/K+-ATPase (NKA) and H+-ATPase (V-ATPase) remained unchanged during TFM exposure in both HW and SW. However a 28% decrease in plasma Na+ in HW and a 10% decrease in plasma Cl- in SW was found in sea lamprey during recovery from TFM exposure. In trout, TFM led to initial Na+ losses, which was compensated by increases in NKA and Total ATPase activity by 6 h in both HW and SW. These initial Na+ loses may be due to an “osmo-respiratory compromise”, where TFM-induced increases in O2 consumption may have lead to increased gill-perfusion and surface area, elevating ion-losses. There was no effect on enzyme activity or expression in sturgeon exposed to TFM in HW, but plasma Na+ dropped by 20% with a 22% increase in plasma Cl- following recovery. No significant effects of TFM on gill structure were observed in all three species. The greater sensitivity of lamprey in SW versus HW can partially be explained by greater susceptibility to ionic disturbances, but other factors are also likely involved. It is concluded that the effects of TFM on gill-mediated ion exchange are minimal and do not translate into substantive disturbances to internal electrolyte balance. However, there is a potential that these effects may persist post-TFM exposure.

Convocation Year

2015

Convocation Season

Spring

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