Effects Of Nitrite In Goldfish (Carassius Auratus) Olfactory Function

Abstract

In the last decade, freshwater ecosystems have experienced a dramatic increase of nitrogenous compounds as a result of farming and industrial activity. Aquatic ammonium (NH4+) is naturally transformed to nitrite (NO−2) by nitrifying bacteria. Nitrite is toxic to vertebrates and is known to cause disruption of physiological processes such as ion homeostasis, respiration, and cardiovascular activity. However, little is known about the effects of NO−2 on the olfactory function in teleost, which is critical for the survival of the species. This study aims to determine the physiological effects of sub‐lethal concentrations of nitrite in the olfactory function of goldfish (Carassius auratus). Thus, goldfish were exposed to 6 different NO−2 concentrations (1000 mM, 500 mM, 300 mM, 100 mM, 10 mM and 0 mM.) for 72 h. At the end of the experiment, blood, brain and nose samples were obtained for histological analysis. Additionally, in order to determine the reduction of olfactory function, olfactory responses to several food odorants were recorded by electro‐olfactogram (EOG) after exposure of the nose to several NO−2 concentrations. No mortality was observed in any treatment. Goldfish exposed to the two highest concentrations of NO−2 exhibited metahemoglobemia (darkening in the blood due to irreversible oxidation of hemoglobin). Histological analysis of the olfactory epithelium showed an increase in mucus production and mucus cells. Moreover, the olfactory epithelia of these fish showed hyperplasia of the olfactory sensory neurons. Hyperplasia of epithelium cells occurred in goldfish exposed to high NO−2 concentrations. Preliminary electrophysiology recordings showed a decrease in the olfactory function due to NO−2 treatments. These results suggest that sub‐lethal concentrations of nitrite are neurotoxic and alter the olfactory function in fish.Support or Funding InformationResearch support: Texas State University start‐up funding to Dr. Mar Huertas.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.