Gill morphology during hypercapnia in brown bullhead (Ictalurus nebulosus): role of chloride cells and pavement cells in acid‐base regulation

The role of gill chloride cells (CCs) and pavement cells (PVCs) in acid‐base regulation was evaluated in brown bullhead catfish ( Ictalurus nebulosus ) subjected to acute hypercapnia (water Pco 2 =15 torr). Chronic (10 day) cortisol treatment was used as a tool to cause CC proliferation to permit a comparison of the regulatory capacities in groups of fish with widely different gill CC populations. Cortisol (4mg kg −1 day −1 ) caused a …