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.