Acid-base balance, osmoregulation and hematological changes in tilapia (Oreochromis niloticus) after sublethal cadmium exposure

Abstract

Tilapia exposed to two different Cd concentrations in freshwater had varying levels of Cd in their gills, with fish exposed to 2 mg/L of Cd having a higher Cd level than fish exposed to 1 mg/L of Cd. The higher Cd level exposure caused considerable metabolic acidosis (lower pH and higher pCO2) and inhibited gill carbonic anhydrase. Fish exposed to higher Cd levels had lower osmolality, levels of plasma Cl− and K+ but constant levels of Na+. All hematological parameters tested in this study, including red blood cells, hemoglobin, hematocrit, and mean cellular hemoglobin concentration hematocrit, decreased as a result of increased Cd exposure. This is consistent with the pO2 measurement, which indicates that fish exposed to greater levels of Cd had a considerable reduction in pO2.