Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

Program Name/Specialization

Biological and Chemical Sciences

Faculty/School

Faculty of Science

First Advisor

Dr. Michael P. Wilkie

Advisor Role

Supervisor (PI)

Abstract

Parasitic sea lamprey (Petromyzon marinus) ingest large quantities of blood from fishes using their oral disc and rasping tongue, most often killing the host. In the early 1900s, sea lamprey invaded the Laurentian Great Lakes, decimating sport, commercial and culturally significant fisheries. Since the early 1960s, chemical control using the lampricides 3- trifluoromethyl-4-nitrophenol (TFM) and niclosamide have helped to reduce sea lamprey populations by 90%. Lampricides are applied to larval lamprey nursery streams targeting many generations of lamprey at once. However, there is concern about the potential adverse effects of lampricides on other fishes, particularly vulnerable lake sturgeon (Acipenser fulvescens) populations. In larval lamprey and rainbow trout (Oncorhynchus mykiss), TFM disrupts mitochondrial function, reducing ATP supply and depleting essential energy reserves such as glycogen and phosphocreatine (PCr), leading to death. Yet, little is known about the physiological effects of niclosamide. The goals of this thesis were to better understand how lampricide exposure adversely affected the physiology of the lake sturgeon, and to compare the physiological effects of niclosamide to TFM in larval lamprey, rainbow trout and lake sturgeon. Accordingly, brain, liver and muscle were collected from larval lamprey, trout and sturgeon exposed to TFM or niclosamide, followed by determination of tissue energy reserves (glycogen, glucose), high energy phosphates (ATP, PCr), and acid-base balance. In larval lamprey, brain was most sensitive to niclosamide, resulting in significant reductions in glycogen. In sturgeon and trout, liver was most sensitive to niclosamide and TFM as characterized by large reductions in glycogen concentration, with lesser declines in brain. Niclosamide exposure also caused notable reductions in muscle glycogen stores and intracellular pH in all three species, which could compromise their capacity to perform vigorous activity in the hours following treatment. In all three species, lampricide-induced metabolic disturbances were corrected within 24 h, suggesting that long-term eco-physiological effects on trout and sturgeon populations were unlikely. However, the demonstrated ability of surviving larval lamprey to completely recover from lampricide treatment could also undermine sea lamprey control efforts by leading to increased numbers of parasitic juvenile sea lamprey that could go on to cause substantial damage to Great Lake’s fisheries.

Comments

TFM, Niclosamide, Toxicology, Sea lamprey, lake sturgeon, rainbow trout

Convocation Year

2021

Convocation Season

Spring

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