Direct Effects of Cadmium and Lead on Growth Rate and Thyroid Hormone Production

This experiment investigated the effects of chronic lead nitrate ((PbNO3)2) and cadmium chloride (CdCl2) exposure on growth rate and thyroxine (T4) production in Rana pipiens tadpoles. Chronic exposure to CdCl2 at doses of 0.4, and 4.0 mg/L were not different than controls whereas at CdCl2 exposure at 40.0 mg/L was shown to retard growth, while chronic exposure to (PbNO3)2 at all doses 3.0, 10.0, and 100 mg/L did not retard growth; however, it caused 80 % of animals to develop spinal deformities. Both growth retardation and deformities leave tadpoles more susceptible to predators, thus possibly contributing to anuran decline. In examining thyroid hormone, the radioimmunoassay procedure did not yield valid results, thus it was not possible to determine the effect of lead and cadmium on thyroxine production