ultrastructure and osmoregulatory function of the branchial chamber in the larvae of dragonfly, libellula lydia (odonata)

the ultrastructure of the cells, na+, k+-atpase activity and immunolocalization were examined in the barnchial chamber of libellula lydia (drury, 1773) larvae. na+,k+-atpase activity and localization were performed through biochemical techniques and immunofluorescence light microscopy using a mouse monoclonal antibody iggα5, respectively. the branchial chamber possesses six pair gills lamellae that extend into the rectal lumen. a thickened epithelial layer and a modified fat body cells layer are present at the base of the each gill lamella. epithelial cells covered by a thin cuticle and they possess apical microvilli and baso-lateral membrane infoldings associated with mitochondria. the cytoplasm of the modified fat body cells is filled with mitochondria, glycogen and a few lipid droplets. the na+,k+-atpase activity was significantly higher (15.36 µm pi mg-1 protein h-1) in the branchial chamber. na+,k+-atpase immunofluorescence staining was observed in the epithelial layer cells of the basal pads of the rectal gill lamellae, with a consistently high immunoreactivity. these findings show that the epithelial cells present cytological features of the ionocytes, a high activity and concentration of na+,k+-atpase, confirming their participation in osmoregulation through active ion exchanges.