Degeneration and death, by apoptosis and necrosis, of the pavement and chloride cells in the gills of the teleost Oreochromis mossambicus

Abstract

Summary. Degeneration and death of branchial epithelial cells were studied in an African cichlid fish. In both fresh water and seawater fish the superficially located pavement cells are sloughed off at the end of their lifecycle. This process is preceded by degeneration via a process of cyto plasmic shrinkage and condensation related to apoptotic (physiologically controlled) cell death. The chloride cells are pleomorphic, i.e., accessory, mature, and degenerating cells. Degeneration of chloride cells mainly occurs by apop tosis. Degenerating cells show shrinkage and densification of cytoplasm and nuclei, and swelling of the tubular system; these cells are then separated from the ambient water by pavement cells. They are finally phagocytosed and digested by macrophages. Apoptosis of chloride cells, but not of pavement cells, is greatly stimulated when the fish are in seawater; this reflects an increase in cellular turnover of the chloride cells. Accidental cell death (necrosis) of pave ment cells or chloride cells is rarely observed in fully adapted freshwater and seawater fish. Its incidence in creases in the first few days following transfer of fish from fresh water to seawater.

Effect of ambient and dietary cadmium on pavement cells, chloride cells, and Na+/K+-ATPase activity in the gills of the freshwater teleost Oreochromis mossambicus at normal and high calcium levels in the ambient water

“…The discrepancy can be explained by the results of our analysis of the ultrastructure of the cells. In earlier studies (Wendelaar Bonga and Van der Meij, 1989;Wendelaar Bonga et al, 1990) we have identified different subtypes of chloride cells: accessory, immature, mature and apoptotic cells -that we have interpreted as successive stages in the chloride cell cycle -and necrotic cells. Because mature cells contain a well developed tubular system and are in contact with the water via the cell apex that frequently is differentiated into an apical pit, the ion-exchange activity of the chloride cells is most likely concentrated in this cell stage.…”

“…The fish were lightly anesthetized in 0.2% 2-phenoxyethanol, and decapitated. The gill filaments were ex cised and prepared for electron microscopy as described by Wendelaar Bonga and Van der Meij (1989).…”

“…The ultrastructure of the branchial epithelium of tilapia has been described earlier (Wendelaar Bonga and Van der Meij, 1989). Briefly, the lamellae are covered by one or two layers of pavement cells.…”

“…The accessory chloride cells of tilapia are considered functionally inactive replace ment cells. They are frequently not in contact with the water and are lacking the apical interdigitations with cytoplasmic processes of neighbouring cells that are typical for accessory cells in seawater fish (Wendelaar Bonga and Van der Meij, 1989). The immature cells may display functional activity in the course of their maturation.…”

Response of club cells in the skin of the carp Cyprinus carpio to exogenous stressors

“…Their ap o p to tic rem nants m ay be removed by neighbouring filament cells, as we observed p h ag o som es in som e of these cells. This is in co n trast with the elim ination of ap o p to tic pavem ent cells, which are shed into the w ater (W endelaar Bonga and Van der Meij 1989;Iger 1992). It is possible that the rem nants of filament cells have nutritional value for the adjacent cells.…”