Temperature tolerance of Penaeus setiferus postlarvae exposed to ammonia and nitrite

The critical thermal maximum (CTM) method was used to determine the acute effect of ammonia, nitrite and the combined effect of both toxicants on the thermal tolerance of white shrimp (Penaeus setiferus) postlarvae. Ammonia did not affect the temperature response of shrimp. Nitrite exposure significantly decreased the temperature tolerance of postlarvae. Coexposure to ammonia and nitrite mixtures modified the CTM; an inverse relationship between ammonia/nitrite toxicity ratios and the CTM was observed. In single exposure, ammonia and nitrite concentrations were related to the mortality rate. No relation was observed between shrimp mortality and the thermal tolerance. Our results suggest that exposure to these nitrogenous compounds can decrease the ability of white shrimp postlarvae to tolerate additional thermal stress.