Zinc Oxide Nanoparticles Impact on Metamorphosis and Thyroid Development in African Clawed Frog

The main purpose of this experiment was to study the effects of ZnO nanoparticles(nps) on the development of Thyroid gland in Xenopus laevis tadpoles throughout the metamorphosis process. To accomplish this, X. laevis tadpoles were exposed to an aqueous suspension of 110--150nm ZnO NPs beginning in-ovo and continuing through metamorphosis up to NF stage 57. The nanomaterials were dispersed through sonication in FETAX salt solution and a static-renewal method was used to replenish the loss of ZnO NPs by precipitation ZnO NPs . All the animals exposed to 0.125 and 0.250 mg/L had the same developmental rate as control, and so were all the other parameters like mortality, follicular area, and hyperplasia. Animals exposed to 0.25 mg/l had moderate levels of hyperplasia (score of 1.4) whereas animals in 0.125 mg/l and control had mild to no hyperplasia respectively. Exposure to 0.5 mg/L and higher ZnO NPs lead to significantly higher mortality, with 2 mg/L inducing a mortality rate of 60%. These concentrations also had significantly smaller average body mass, the rate of the metamorphosis of tadpoles and the thyroid gland development in the exposed tadpoles. The average follicular area for these tadpoles was smaller than controls, and the follicular area of animals in control increased by 90% of the area of animals in 2 mg/L at the end of the study period. The transformation of simple cuboidal epithelium in follicle walls of control to tall columnar cells in 0.5mg/L and higher concentrations indicate some degree of hypertrophy. No tadpoles exposed to concertation above 0.500mg/L reached stage 57, and the average stage for the animals in 2mg/l was 47, indicating that higher doses have a detrimental effect on thyroid gland development in Xenopus laevis.