Energetic Costs of Detoxification. Environmental challenges can invoke additional energy expenditures at the expense of growth or reproduction by increasing the costs of maintenance and subsequent reductions in surplus power. One such environmental factor, for which we know little in terms of energetic cost but which may have important energetic ramifications to organism fitness, is exposure to foreign compounds or xenobiotics. Our research is investigating the specific costs of detoxification reactions and the potential physiological trade-offs between the costs of detoxification and growth or reproduction. Our research in this area will: 1) aid in an understanding of xenobiotic detoxification costs, 2) determine if detoxification costs can affect fitness through energy trade-offs, and, 3) lead to a more comprehensive understanding of the relationship between the fate of xenobiotics in fish and their ecology and life history.
Environmental and life history modulators of contaminant fate and toxicity. Organisms are in open, dynamic equilibrium with their environment and the responses to one environmental factor must be rationalized with the requirements to deal with other impingements. Currently we are examining the effects of temperature and salinity on the toxicokinetics (uptake, distribution, metabolism and excretion) of the model carcinogen beno[a]pyrene in salmonids. As well, we are examining the effects of life history on toxicant sensitivity. For example, prior to or accompanying the seawater migration of some salmonids, a process known as smoltification occurs, which consists of a spectrum of changes resulting in adaptations for a marine existence. Our research is focussed on how these developmental processes modify the toxicokinetics and toxicodynamics of xenobiotics in these fish, and to relate these changes to biochemical and physiological processes which occur during smoltification.
Other recent work in our laboratory suggest that toxic threshold values developed for selenium using warm-water species of fish may not be generally applicable to salmonids such as the cutthroat trout, or other cold-water species. We are currently examining the mechanisms behind Se tolerance in Cutthroat trout populations which have evolved in seleniferous habitat.
Contaminants and Stress. Organisms such as fish must be able to adapt to dynamic or changing environments, which include both natural and anthropogenic chemical stressors. The actions of stressors are two-fold; 1) they produce effects which disturb homeostasis, and 2) they elicit a set of coordinated responses which compensate for the disturbances, i.e. they are adaptive, enabling the animal to overcome the threat. This response is generally accepted as stress, which evokes in an animal an organismal (e.g. neuro-endocrine) and cellular (e.g. heat shock proteins) response. Our research in this area is focussed on examining the effects of pollutants on eliciting and negating the stress response in fish, and in quantitating the effects on the whole organism. As well, our research in this area is concentrated on understanding the impacts of the stress response (or its absence) on organism fitness and the neuroendocrine mechanisms underlying the impacts on other physiological systems.
Ecologically-relevant Sublethal Toxicities. The current use of pesticides, including those in the agriculture and aquaculture industry, are an emerging issue of concern for the environmental health of anadromous salmonids in BC. The consequences of pesticide exposures for salmon health and fitness are largely unknown. We are specifically focusing on several classes of pesticides which target the nervous system. Recent evidence from our laboratory has shown that olfactory receptor neurons are especially sensitive to compounds with these mechanisms of action, which include the organophosphate and carbamate pesticides. Our research centers on the salmon olfactory system as a sensitive indicator of sublethal neuro-physiological and behavioral toxicity. There are established relationships between olfactory function and the performance and fitness of individual salmonids. Effects on olfaction can affect many aspects of fish behaviour including predator avoidance, imprinting, homing behavior, and reproductive priming. Our approach has two key elements: 1) to determine the toxicological effects of environmentally realistic pesticide exposures on the normal function of the salmonid olfactory system, and 2) to evaluate neurological impairment in the context of salmon fitness. These results should provide empirical data on a poorly understood and potentially critical aspect of salmon habitat quality in the waters of BC.
Links:
American Fisheries Society: Physiology Section
Physiology Section AFS: International Congress on the Biology of Fish
Aquatic Toxicity Workshop
The Society of Environmental Toxiology and Chemistry
News Article on Our Olfactory Research
