CHANGES IN ULTRASTRUCTURE OF THE ANAL PAPILLA EPITHELIAL-CELL OF AEDES-TOGOI THEOBALD, A SEA-WATER MOSQUITO, IN ADAPTATION TO DIFFERENT SALINITIES

The anal papilla epithelial cell at the mid-4th instar of Aedes togoi, a salt-water mosquito, was examined for ultrastructural changes in adaptation to deionized water or to highly concentrated artificial sea-water. Larvae were hatched in tap-water, and then transferred to one of the other media. In larvae which had been in either of the new media for the final 20 min before samples were collected, the response was adhesion of apposed apical infold membranes. In larvae which had been in concentrated sea-water for the final 3 hr, apical membranes and subcuticular matrices, were endocytosed and digested by large and numerous lysosomes, and membrane surface was greatly decreased. In those which had 2.5 hr adaptation, in deionized water, many rough endoplasmic reticula and Golgi apparatus appeared, and mitochondria remained in the infolding area even in the presence of membrane adhesion. At 48 hr adaptation, adhesion was absent and membrane was increasing. The increase continued through longer periods of adaptation until, at 10 days, apical infoldings were producing secondary folds. These findings suggest that the anal papilla functions to resist influx of salt in an environment of high salt concentration, and to promote influx of salt in an environment of low salt cocentration.