Structure, transduction pathway, behavior and toxicity of fish olfactory in aquatic environments

Abstract

The olfactory system in teleost fish plays a vital role as chemosensory organ that directly interacts with the aquatic environment, exhibiting high sensitivity to chemical alteration in aquatic environments. However, despite its importance, there has been a lack of systematic reviews in the past decade on fish olfactory structure, transduction mechanisms, and the impact of environmental pollutants on olfactory toxicity. This study analyzed 272 relevant studies, focusing on the role of the olfactory system and the disruption of olfactory function by contaminants. Fish processes odors through olfactory receptor neurons, olfactory nerves, mitral/ruffed cells, glomeruli, and neurotransmitters, mediated by membrane potentials resulting from ion channels in the olfactory epithelium and olfactory bulb, which are then relayed to higher brain regions via the medial olfactory tracts and lateral olfactory tracts for further integration and modulation. This process minimizes the overlap between complex odor sets, ensuring distinct representation of each odor and eliciting appropriate olfactory-mediated behaviors, such as feeding, migration, alarm responses, and reproduction. Current research identifies four main types of contaminants affecting the fish olfactory system: heavy metals (51.60 %), organic contaminants (33.79 %), acidification (12.33 %), and salinity (5.94 %). The main mechanisms of impact are: morphological changes (21.19 %), alterations in olfactory receptors (29.24 %), damage to olfactory receptor neurons and neurotransmitters disruption (26.69 %), plasticity (2.97 %), and defense mechanisms (19.92 %). We also identify uncertainties and proposes future research directions on the effects of contaminants on fish olfactory. Overall, this review provides valuable insights into the toxicity of contaminants on fish olfactory.