engleski

Ultrastructural changes in gill lamellar epithelium of Wels catfish Silurus glanis adapted to brackish water

Gill epithelium of fish is a dynamic ion transporting mechanism that consists of mitochondria rich cells (MRC) ; pavement cells (PC) ; and mucous cells (MC). In freshwater, MRC are the ones implicated in active uptake of Cl- induced by Na+/K+-ATPase pump located in the basolateral part of cell plasma membrane. Wels catfish Silurus glanis was held in closed experimental recirculation systems ; two groups were maintained for 51 day at constant temperature of 26°C at two different salinities - freshwater (0.3 ‰ ) and brackish water (11 ‰ ), respectively. At the end of the experiment, gills were sampled for routine histology, TEM, SEM and immunocytochemistry, in order to describe ultrastructural changes as well as to localize ATP-ase α -subunit activity induced by the environmental change. S. glanis gill structure shows typical presence of MRC located in interlamellar epithelium both in freshwater and brackish environment, similar to the distribution observed in other freshwater-adapted species. In brackish water however, dark MR cells go through degeneration and necrosis process, while small and compact immature cells with dark cytoplasm resembling β MR cells, are frequently observed tightly enveloped by α MR cells. Evaluating overall appearance and functionality of S. glanis gill epithelium, we conclude that even though it shares many characteristics with other euryhaline fish, it also shows peculiar process of differentiation and maturation of β MR cells enclosed by the cytoplasm of pale MR cells.

epithelium; gill; ultrastructure; Wels catfish

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