Ongoing Research Projects
(i) Mechanisms of Ammonia Tolerance & Nitrogen Excretion in Fishes.
can arise in aquatic environments due to the degradation of organic matter,
run-off from agricultural operations or as leachate from landfill sites. In humans, neurotoxic ammonia can build-up in
the body due to defects in the liver’s ability to detoxify ammonia arising from
protein catabolism. In a collaborative
effort with Dr. Les Buck (Department of Zoology,
We are also studying how wastes, such as ammonia urea, are excreted across the gills of primitive fishes such as the lamprey. Using different surgical, pharmacological and molecular approaches a major goal is to determine how the parasitic lampreys rid their bodies of urea and ammonia after ingesting the blood of fishes. Unlike filter feeding larval lampreys, the parasitic lampreys use an oral disc to attach to their hosts, and use their rasping tongue to pierce the hide and then suck the blood from the fish. We recently reported that parasitic lampreys excrete vast quantities of urea after feeding on sharks, which suggest that they have specialized urea transporters for this purpose.
Much of this work is presently being conducted by two undergraduate honours thesis students, but there are opportunities for an M.Sc. student to use cell culture and neurophysiological techniques to learn more about the mechanisms of ammonia toxicity and survival in fishes, or two examine modes of urea excretion in lampreys.
(ii) Mechanisms of Anoxia Tolerance in the Goldfish.
Unlike most vertebrates, in which oxygen starvation can rapidly lead to brain damage or death within minutes, the goldfish readily survives in oxygen depleted environments for days or even weeks. In an ongoing collaboration with Dr. Buck we measured the electrical properties of goldfish brain slices in response to anoxia using whole cell patch clamping. We have observed that the brain of some fish is protected by decreasing the activity of N-methyl-D-aspartate (NMDA) receptors, which are normally involved in processes such as learning and memory, and other ATP consuming enzymes (e.g. Na+/K+ ATPase)
Much of the work so far was completed by honours thesis students, but there are opportunities for an M.Sc. student to use cell culture, immunodetection and neurophysiological studies to learn more about the neurophysiology of domestic and pond-dwelling goldfish during periods of oxygen starvation.
(iii) The Effects of Multiple Metal Interactions and Dissolved Organic Matter on Fish Gill Function.
Although substantial progress has been made in recent years to understand how fish gills respond to metals on an individual basis, rarely are fishes exposed to metals or other toxicants individually. Since most toxicants exist in mixtures, a fundamental goal of my lab is to determine how mixtures of metals alter gill mediated physiological processes such as ion regulation in rainbow trout (Oncorhynchus mykiss). This work uses the Biotic Ligand Model (BLM), which provides details about each metal’s gill binding affinity, to predict how metals such as Cd, Pb and Zn interact with the gill. To test predictions using the BLM, fish survival and gill metal accumulation on the gill are then measured. Gill mediated physiological processes such as ion (Na+, Cl-, Ca2+) uptake are also measured to determine if the physiological responses of fishes can be predicted by the BLM. Dissolved organic matter (DOM) reduces gill metal binding, but different metals have different binding affinities for this ligand. Thus, a longer term goal is determine how the presence of DOM influences fish survival and gill function in fishes exposed to different combinations of metals.
We presently have two M.Sc. students and a Postdoctoral Fellow doing work in this area, but there are opportunities for undergraduate projects.
(iv) Modes of Lampricide Toxicity in Larval Sea Lampreys and Non-target Fishes
work, funded by the Great Lakes Fishery Commission, is investigating how the
lampricide 3-trifluoromethyl-4-nitrophenol (TFM) exerts its toxic effects in
fishes. This pesticide is added to streams containing larval sea lampreys as a
means to control populations of this invasive species which have plagued
fisheries in the
We presently have one M.Sc. student working on the physiological effects that TFM has on trout and larval lamprey physiology. There is an opportunity for another M.Sc. student, however, to conduct studies on the routes and mechanisms of TFM entry into fishes in order to further refine TFM application techniques.
(v) Use of Passive Integrated Transponder (PIT) Tags to Monitor the Movements of Brown Trout in the Grand River Tailwater.
In a collaborative effort with the Friends of the Grand
River (FOGR), Grand River Conservation Authority, and the Ontario Ministry of
Natural Resources (OMNR), the long-term goal of this work is to use surgically
implanted passive integrated transponder (PIT) tags to determine if habitat
improvement measures (e.g. placement of large cover) are being used by brown
trout (Salmo trutta) in the Grand
River Tailwater. Another important goal
is to use this technique to determine how/if brown trout survival over the
winter is affected by limited habitat availability and ice formation. It is
suspected that poor over-winter survival is one factor that makes it necessary
to annually stock brown trout into the Grand River Tailwater to sustain this
internationally recognized fly fishery. This pilot study is designed to assess
the feasibility of using a portable PIT tag detector unit to locate fish in the
There may be an opportunity for further field and laboratory work on PIT tagging in trout by an undergraduate student.