Morpho-functional alterations in the olfactory system of rainbow trout (Oncorhynchus mykiss) and possible acclimation in response to long-lasting exposure to low copper levels

Abstract Morpho-functional changes in the olfactory system of Oncorhynchus mykiss were investigated at different times during a 40-week exposure to either 20 μg Cu 2+ /l (20-μg group) or 40 μg Cu 2+ /l (40-μg group). Histopathological alterations in the olfactory epithelium of the 20-μg group were moderate, whereas those in the 40-μg group were more severe and intensified with time exposure. The 20-μg group exhibited some olfactory discrimination ability but presented higher sensitivity thresholds than controls. The 40-μg group became unresponsive with time, even to a water inflow 4 times more odor concentrated. The time frame for morpho-functional recovery after returning to well water was dose dependent. Morpho-functional alterations in response to a 20 μg Cu 2+ /l exposure appeared less important and the functional recovery shorter in adults compared to what has been previously observed in younger fish. Fish acclimation in conditions of long-lasting exposure to each copper dose is discussed.