Xenopus metamorphosis after neonicotinoid exposure

Xenopus laevis tadpoles were held in 4 replicate vivaria for each of 4 treatments of neonicotinoid pesticides and one control treatment for at least one month (Control media, thiamethoxam high concentration of 100 ppm, thiamethoxam low concentrations of 20 ppm, clothianidin high concentrations of 100 ppm, and clothianidin low concentration of 20 ppm). Water was sampled for chemical testing on Day 33. Between Day 1 and 44, instantaneous measures of length were collected on a random selection of tadpoles from each vivarium. On Day 44, tadpole length (mm), weight, and developmental stage (Nieuwkoop-Faber staging) were measured for all tadpoles in all vivaria (three of the measured individuals from each replicate treatment group (total n=12 for each treatment) were vivisected and liver, brain, and somatic tissue frozen in RNA/DNA shield for qPCR analyses for another study). On Day 44, tadpoles (n=5) which had reached NF stage 57 were transferred to other vivaria and remained in their original treatment solution through Day 76; these animals were monitored until metamorphosis.