Haematological responses of larval Rana catesbiana to sub-lethal nitrite exposures

Nitrite-induced methaemoglobin formation has been reported for various fish, and the authors have now carried out experiments to determine whether bullfrog tadpoles (Rana catesbiana) would develop methaemoglobin when exposed to nitrite and, if so, whether any protection against methaemoglobinaemia is offered by increased ambient chloride concentrations. The results indicate resistance to nitrite toxicity in tadpoles is an uptake phenomenon. Tadpoles show gill ion absorptin similar to fish; tadpoles at the late larval stage have limited gill surface area and thus a lower dose response would be expected. This could also account for the increased efficacy of chlorides as a protection against nitrite toxicity.