The Sensitivity Of Frog(Xenopus Tropicalis)and Zebrafish(Danio Rerio)Embryos To Organotin Compounds

In the environmental toxicology, xenobiotics usually show different toxicity in different developmental stages of organisms. Different species, including the closely related species, usually show different responses to the same special pollutant. However, there are not adequate studies on the stage-specific sensitivity of the same species and the sensitivity of different species to the same contaminant. Tributyltin (TBT) and triphenyltin (TPT) are the most important organotin compounds. They have been proved to have strong teratogenic effects on amphibian and fish embryos. In this paper, we studied the sensitivity of Xenopus tropical is and zebrafish embryos to organotin compounds.Firstly, Xenopus tropicalis embryos were exposed to200ng/L tributyltin (TBT) during different periods. More than90%embryos showed malformations in treatment groups. The main characteristic malformations were abnormal eyes, enlarged proctodaeum, narrow fins or absence of fins, and bent tails. Compared with the control, the eyes were smaller in the2nd d and bigger in the3rd d treatment groups. The dorsal fins were a little narrower in the1st d treatment group, both dorsal and ventral fins were much narrower with tail-tip residue or gap near the proctodaeum in the2nd d treatment group, and the fins were slightly narrower in the3rd d treatment group. Our results suggest that the malformations in the eyes and fins were more variable during different exposure periods.Secondly, we further exposed X. tropicalis embryos to TPT (5-15μgSn/L) during different stages. Severe malformations were observed in the embryos after exposure to5-10μgSn/L TPT during S32-40and S40-46. The most characteristic malformations were narrow or no fins, followed by enlarged proctodaeums and skin hypopigmentation. The sensitive window of fin defects indicated that TPT affected the formation rather than induction or expansion of fins. Our results suggest that TPT-induced teratogenicity was highly stage-specific.Finally, zebrafish embryos were exposed to TPT (1～10μgSn/L) during different periods. Our results suggested that triphenlytin induced multiple malformations including deformed eyes, bent notochords, bent tails, and edema in hearts after5d exposure at concentrations of1-10μgSn/L. In contrast, no discernible malformations were observed in TPT-treated groups after each separate day exposure. Our results also suggest that TPT-induced teratogenicity was not stage-specific.In brief, our results suggest that the teratogenic effcts of organotins on X. tropicalis were highly stage-specific and that the sensitivity of X. tropicalis and zebrafish to organotins were much different. The present study not only indicates that it is important to take sensitivity of stages and species into the ecological risk assessment of contaminants but also provides basis for mechanism study of organotin-induced teragogenicity.