Effects of glyphosate on growth rate, metabolic rate and energy reserves of early juvenile crayfish, Cherax quadricarinatus M.

Abstract

Early juveniles of the crayfish Cherax quadricarinatus were exposed for 60 d to 10 and 50 mg/L of pure glyphosate (acid form) in freshwater. Mortality was 33% at the highest concentration, while no differences in molting were noted among treatments. Weight gain was evaluated every 2-wk throughout the assay. At the end of the experiment, glycogen, lipid and protein levels were determined in both abdominal muscle and hepatopancreas. Besides, both pyruvate kynase and lactate dehydrogenase activity were measured in the same tissues, while both alanine (ASAT) and aspartate (ALAT) aminotransferase levels were measured in hemolymph. After the first month of exposure, weight gain was significantly (p<0.05) reduced at 50 mg/L. At the end of the assay, lipid levels in muscle, as well as protein level in both hepatopancreas and muscle were significantly (p<0.05) reduced. These results indicate a long term utilization of both lipid and protein as main energetic reserves, likely to face the chronic stress represented by the exposure to the herbicide. Besides, the lower pyruvate kynase activity in muscle suggests a possible metabolic depression in this tissue. The hemolymphatic ASAT:ALAT ratio showed higher levels than control at the highest glyphosate concentration, indicating a possible damage to several tissues