The stomachs of most vertebrates operate at acidic conditions, which is thought to be an important evolutionary feature to protect from environmental pathogens. Interestingly, extreme stomach pH is also found in the larvae of many ambulacraria (echinoderms & hemichordates). These larval stages can have a stomach pH up to 10.5. In echinoid larvae, gastric alkalization is driven by Na+/K+-ATPase (NKA) and V-type H+-ATPase expressed in stomach epithelial cells. Gastric alkalization in hemichordate larval stages is also driven by the NKA and by an omeprazole sensitive mechanism indicating the employment of H+/K+-ATPases.
Current research aims at improving the model for gastric alkalization using protein biochemical and molecular approaches as well as ion selective electrodes to measure gastric pH. Furthermore, gastric alkalization may represent a key trait in ambulacraria larvae that determines their sensitivity to ongoing ocean acidification. Here my research aims at disentangling the energetic costs of key physiological processes (gastric alkalization & biomineralization) in these larval stages.