Do Lithobates catesbeianus tadpoles accimatise to sub-lethal copper?

The aim of this work was to study the acute effects of short-term exposure (96 hours) to sub-lethal concentrations of copper (2 and 3 mg L−1)on ecotoxicological stress biomarkers in the aquatic stages of Lithobates catesbeianus (syn. Rana catesbeiana) larvae. To this end, the effects of copper on brain acetylcholinesterase, liver and gill catalase and glutathione-S-transferase activities were examined. In addition, the changes in gill structure were monitored by scanning electron microscopy. Neither the survival nor the activity of the biomarker enzymes was affected by copper; however, the gills were affected, exhibiting alterations in the epithelial cells of the tufts. The results were interpreted as evidence that, at the concentrations assayed, there may be an acclimation of the tadpoles to copper; the anomalies observed in the epithelium of the gills may be compatible with the survival of the animals since at their developmental stage the skin plays an important role in the respiratory function.