RESUMO
The uptake of heavy metals like mercury is rapid and tissue and cell pathologies are a consequence of its concentration in water and the time of exposure. For Trichomycterus brasiliensis, inorganic mercury is lethal above 0.1 mg.l(-1) in 24 hours. The gills were severely affected: an increased cell proliferation in the interlamellar regions leads to a thickening of the secondary lamellae. The lamellar fusion is higher 12 hours after exposure. The liver is increasingly damaged: after 4 hours the hepatocytes show hyaline sites around the nuclei proliferation of smooth ER, modified mitochondria and less electron dense nuclei without nucleolus. After 24 hours, necrosis is almost complete and blood comes out of all capillaries. The kidneys are also disorganized and tubule cells decrease in number and change in size, but there is a tendency of tissue recovery after 24 hours. Nerves such as the optic, show disorganized disposition of axons and mainly disruption and dissociation of myelin sheaths, leading to a decrease in motility and coordination. All these results demonstrate that T. brasiliensis is severely affected by inorganic mercury in concentrations that are sublethal for many other species.
Assuntos
Peixes/metabolismo , Cloreto de Mercúrio/toxicidade , Animais , Brânquias/efeitos dos fármacos , Brânquias/patologia , Rim/efeitos dos fármacos , Rim/patologia , Fígado/efeitos dos fármacos , Fígado/patologia , Atividade Motora/efeitos dos fármacos , NataçãoRESUMO
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.