Effect of mercury on the fish (Alburnus alburnus) chemoreceptor taste buds. A scanning electron microscopic study.

Taste buds (TBs) were investigated by scanning electron microscope on various parts of the oral cavity of the bleak. (Alburnus alburnus) after differently long exposures to mercury (300 micrograms/l Hg++). This low concentration of mercury did not result in lethal effect on the bleak even after 19 days long exposure, but produced morphological changes on the TBs, which showed duration dependency. The first sign of the morphological alteration on the TBs was observed after three days long exposure, when the microridge system of the epithelial cells became damaged and the mucus secretion increased on the apical surface of the TBs. On the TBs exposed for 10 days swollen microvilliar tips of the sensory cells could be observed besides the damage of the epithelial microridge system. On the TBs exposed for 19 days degenerative changes were detected on the microvilliar system of both the supporting and receptor cells. By this time completely degenerated TBs were frequently observed.