This postdoctoral project is a continuation our line of research that has been supported by FAPESP in which we investigate the gill (Na+,K+)-ATPase in crustaceans as molecular marker of adaptation to environments of different salinities. Freshwater species face the challenge to develop physiological adaptations under hyposmotic conditions. In hyperosmoregulating animals, the gills act as a selective interface that actively absorbs Na+ and Cl- ions from the dilute external media to the hemolymph; the (Na+, K+)-ATPase and V-ATPase are key molecules in this process with other transporters being present in the basolateral and apical membranes. Ucides cordatus is naturally exposed to wide fluctuation in salinity, from 2 to 33 0, mainly resulting from tidal flow in mangroves. These salinity changes (either increase or decrease) can affect the expression/activities of the antioxidant enzyme system, the ion transporting enzymes, and oxygen consumption. In this project we will study the activities of the above enzymes, aiming to understand the mechanisms involved in the biochemical, physiological and molecular adaptations during the invasion of the freshwater environment by crustaceans, and in ammonium excretion, using the mangrove crab U. cordatus. To characterize osmoregulatory capacity in U. cordatus, crabs will be acclimated to 2 0, 26 0 and 34 0 salinity for ten days. For each acclimation condition the following steps will be performed: 1) evaluate the (Na+,K+)-ATPase, V-ATPase, Ca2+-ATPase and carbonic anhydrase activities; 2) examine the modulation of each activity by their respective(s) effector(s); 3) effect of specific inhibitors; 4) ammonium excretion; 5) phosphoenzyme formation; 6) effect of FXYD on (Na+,K+)-ATPase activity; 7) ionic concentration and hemolymph osmolality; 8) mRNA expression of ± and B subunits of (Na+,K+)-ATPase and V-ATPase; 9) oxygen consumption; 10) estimate activity of oxidative stress enzymes; 11) evaluate the effect of both K+ and NH4+ on (Na+,K+)-ATPase activity and phosphoenzyme formation; 12) evaluate (Na+,K+)-ATPase activity after acclimation to different ammonium sulfate concentrations; 13) immunohistochemical localization of (Na+,K+)-ATPase and V-ATPase.
News published in Agência FAPESP Newsletter about the scholarship: