UC San Diego

The movement of ions across a cell membrane is critical to a wide variety of physiological functions across all phyla, however, little research has been conducted on ion transport in Cnidarians. Understanding coral physiological mechanisms is of increasing interest, however, due to mounting environmental stress. Two key ion transport dependent processes are calcification and photosynthesis by the endosymbiotic algae. This study utilized fluorescent immunostaining to localize two key ion transport proteins in three species of scleractinian corals: Acropora yongei, Stylophora pistillata, and Pocillopora damicornis. Proteins investigated included vacuolar hydrogen -ATPase (VHA) and sodium-potassium ATPase (NKA). VHA was localized to the intracellular symbiosome membrane of endodermal cells, providing supporting evidence for its participation in a carbon concentrating mechanism (CCM). This localization was conserved in all three species of coral. VHA was also localized in the aboral endoderm, and was more abundant in the growth tips of corals, suggesting it may play a role in facilitating rapid calcification by aiding in pH regulation. NKA was observed in the calcifying epithelium of all three species. However, it was found in the apical membrane of the oral ectoderm of A. yongei, only. The similar localization of NKA in the calcifying tissue suggests it plays a conserved role in calcification, while the differences in location between other tissues indicate that corals have evolved diverse ion transport mechanisms for other functions. These differences may lead to differential responses to environmental stressors