Acute Effects of Mercuric Chloride on the Olfactory Epithelium of Trichomycterus brasiliensis

The olfactory organ in fish has a distinct localization, a major biological significance, and an important role in fish behavior. One group of Trichomycterus brasiliensis was exposed to two different concentrations of mercuric chloride (0.05 and 0.1 mg HgCl2 liter−1). The surface of the olfactory epithelium was investigated with scanning electron microscopy. Forty individuals were used in this study. The olfactory epithelia were collected after 4, 12, 24, 48, and 96 hr from contaminated and control aquaria. In the experiment with 0.1 mg HgCl2 liter−1 all individuals died within 24 hr with significant damage to the olfactory epithelium. Type 1 ciliated cells were the most evidently altered. With 0.05 mg HgCl2 liter−1 the initial alterations were considerable, but after 96 hr the epithelial surface recovered its initial appearance compared with the control individuals. This recovery is due to the resistance of this species and to the decrease in the Hg2+ concentration in water. Therefore, the alterations observed in this study reveal that inorganic mercury affects the olfactory organs structurally, with evident interference with normal behavior.