TSAI, Y-C.; LIN, H-C.; Dep. of Life Science, Tunghai University, Taichung, Taiwan; Dep. of Life Science, Tunghai University, Taichung, Taiwan: The Roles of H⁺-ATPase and Na⁺, K⁺-ATPase in the Gills of Euryhaline Crabs during Salinity Acclimation

Crabs widely distribute through aquatic to terrestrial habitats and are excellent materials to study morphological changes and physiological adaptation. The hemolymph osmoregulatory ability in brackish water or freshwater is crucial for a successful terrestrial invasion. There are several enzymes involved in the osmoregulatory process, including at least Na⁺, K⁺-ATPase and H⁺-ATPase. Na⁺, K⁺-ATPase provides the driving force to establish an ion gradient across the epithelial cell membrane in marine crabs but not necessarily in the freshwater ones. Instead, the driving force may come from apical H⁺-ATPase by generating the H⁺ ion gradient to facilitate the ion flow. In this study, we chose 12 species from two families. First, using the immunohistochemistry method to clarify the distribution of H⁺-ATPase, we divided them into 3 different groups. Next, we correlated the localization of H⁺-ATPase with the variation of Na⁺, K⁺-ATPase activity among 12 crab species between salinities. The crabs that had the cytolasmic H⁺-ATPase had a significantly greater Na⁺, K⁺-ATPase activity difference than those species that have an apical H⁺-ATPase distribution. The third part of our study is to estimate the H⁺-ATPase activity of Uca formosensis, the species known to have a stable Na⁺, K⁺-ATPase activity during salinity changes. The H⁺-ATPase activity of 5 ppt acclimated crabs was almost significantly higher than that of 35 ppt ones. However, the protein level of H⁺-ATPase was not significantly different between salinities. In conclusion, our results supported the hypothesis that H⁺-ATPase plays an important role in the freshwater adaptation in branchyuran crabs.