Ultrastructural alterations of the dogfish {Scyliorhinus canicula L.) gill filament related to experimental aquatic zinc pollution

Abstract

Effects of dissolved Zn on the structure of th dogfish gill filament were investigated. Ulstrastructural alterations were seen only in chloride cells, probably due to an accelerated turnover. Following exposure to ZnSO sub(4) (15 ppm Zn) for 2 wk, varying degrees of electron density of the cytoplasmic matrix were observed among the chloride cell populations. Two cell types, which were not found in untreated fish are described: dark cells, highly electron dense and smaller in size than chloride cells of untreated animals and cells packed with swollen mitochondria, which are probably undergoing degeneration. The authors suggest that these alterations are due to an osmotic stress caused by Zn ions. Proliferation of chloride cells following Zn treatment described in a previous light microscope study might be explained as a compensatory response to restore altered osmoregulatory capacities.