Contaminant effects on chemical communication in aquatic animals: targeted effects and recovery during continuous exposure conditions

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The long-term objective of my research is to understand the causes and consequences of contaminant-induced impairment of chemical communication systems among aquatic animals. These animals use smells to avoid predation, find food, or reproduce. Infomolecules, in the form of amino acids (food and migratory cues), pheromones (sex cues), or bile acids (predator cues), are perceived by the olfactory system and trigger stereotypical behavioural responses. Environmental contamination can interfere with olfaction leading to a maladaptive condition: 'infodisruption.' Contaminant-induced infodisruption is known to affect many species exposed to environmentally-relevant contaminant concentrations under lab and field conditions. Three subpopulations of olfactory sensory neurons (OSNs) occur in fish: ciliated, microvillous, and crypt cells that are sensitive to bile acids, amino acids, or pheromones, respectively. Different molecular mechanisms are used by different OSN-subtypes, allowing us to differentiate which OSN-subtype is responsible for processing specific odours. We have established that metals target OSN subtypes which affect specific behaviours. In wild populations, a fish's sensitivity to a particular smell may be affected by ecological context. For example, fish may be hypersensitive to food cues when food is scarce because of increased microvillous OSNs. Conversely, fish in environments contaminated by substances that target ciliated OSNs may not be able to detect and avoid predators. The objectives of this research are: (i) To establish the relationship between specific OSN-subtype dysfunction and behavioural effects in fish, (ii) to determine if ecological context or physiological state can compensate for contaminant effects on olfaction, (iii) to determine if recovery in fish or invertebrates occurs during continuous exposure, and if so, to determine the mechanism of recovery (iv) to determine if natural populations adapt or compensate for contaminant-induced chemosensory deficits. The experimental approach is to study both lab-reared and wild fish and aquatic invertebrates under controlled and field conditions. Chemosensory function will be measured using well-established behavioural and neurophysiological techniques (i.e., electro-olfactography; EOG). Pharmacological agents will be used to determine OSN involvement in the detection of specific cues. The significance of this work lies in understanding the vital role of chemical communication systems in aquatic ecosystems, and the associated risk to aquatic animal populations inhabiting environments contaminated with even very low concentrations of metals. Because chemical communication systems mediate behaviours associated with survival, growth, and reproduction, info-disruption can lead to maladaptive effects that can have important ramifications to the entire ecosystem.**