Environmental Effects Of Nitrite On Goldfish (Carassius auratus) Communication
Martinez, Melody A.
Increased agriculture and industrial activity have elevated concentrations of nitrogenous compounds in aquatic ecosystems. Exposure to elevated nitrite concentrations disrupt physiological and endocrine processes such as ion and hormone regulation, respiratory, and cardiovascular activity. However, there is a lack of research in the effects of nitrite on sensitive organs such as the olfactory epithelium. Fish olfactory systems are highly sensitive and can detect odors in the picomolar concentration. Odorant signals are integrated in the brain and trigger vital physiological functions (e.g. reproduction and feeding) and behavior. Therefore, disruption of the olfactory system will have a cascade of effects, affecting the viability of species in the short or long term. To detect odors, this specialized sensitive organ is continuously exposed to the aquatic environment, making it highly susceptible to toxins like nitrite. We hypothesize olfactory tissue will be adversely affected by nitrite. Thus, nitrite will accumulate and structurally alter the olfactory organ, which will change behavioral responses to odors and therefore act as a neurotoxin. The goal, to determine the acute and chronic effects of nitrite and its accumulation in the olfactory system and vital organs in goldfish. To test our hypothesis, three experiments were conducted; acute nitrite exposure, chronic nitrite exposure, and behavior assessments on chronically exposed fish. Acute exposure fish were exposed to nitrite concentrations (0, 0.3, 1.0, and 10 mM) for 5 days. Chronic exposure fish were exposed to nitrite concentrations (0, 0.01, 0.1, and 1.0 mM) for 69 days. Behavioral assessments were conducted on fish chronically exposed to nitrite concentrations (0, 0.01, 0.3, and 1.0 mM) for 28 days. In both experiments gill, nose and brain was collected for biochemical and histological analysis and nitrite accumulate was significant in acute and chronic experiment. Histological analysis showed an inflammatory process and cellular alteration in acute and chronical exposure. Behavioral assessment showed a decrease in food odor preference after nitrite treatments. Results demonstrate that environmental nitrite concentrations are potentially acting as a neurotoxin that alters olfactory function.
Olfaction, Goldfish, Fish Behavior, Nitrite, Neurotoxin, Neurotoxicology
Martinez, M. (2020). <i>Environmental effects of nitrite on goldfish (Carassius auratus) communication</i> (Unpublished thesis). Texas State University, San Marcos, Texas.