If you have ever had a fish tank, you may be familiar with monitoring ammonia levels in the water. Ammonia levels can rise due to overcrowding, overfeeding, as well as fish waste. Nitrite levels in the water also require monitoring as nitrite can bind to hemoglobin, which prevents oxygen from binding. In effect, by preventing oxygen from binding, the fish can succumb to hypoxia.
Hannah Hughes, a graduate student working in the laboratory of Dr. Mar Huertas at Texas State University, presented research examining the effects of even short term exposure to nitrites on the sense of smell (olfaction) in Monterrey platyfish, Xiphophorus couchianus, at the 2022 Experimental Biology conference last month. Fish are very sensitive to odor molecules and can detect smells over long distances. This ability to detect smells is important for foraging, migrating, as well as coordinating reproduction. Fishermen often capitalize on a fish’s keen sense of smell by placing particularly stinky bait on their hooks.
Hannah and Dr. Huertas found that exposing Monterrey platyfish to nitrites for only 2 days caused inflammation in the olfactory organ of the fish. In addition, fish that had been exposed to nitrites had difficulty detecting smells in a water maze whereas fish that had not been exposed picked the side with the food smell.
H Hughes, M Huertas. Morphological description of olfactory organ changes after acute nitrite exposure in Xiphophorus couchianus. 2022 Experimental Biology meeting abstracts.