Toxic Effects of Tributyltin, Triphenyltin, and SnCl2 on the Development of Zebrafish (Danio rerio) Embryos

Tin (Sn) is one of the heavy metals to which various functions in biological development are attributed in small quantities, for example, a role in cell structure, enzyme activities, and protein and carbohydrate metabolism in fish. Tributyltin (TBT) and triphenyltin (TPT) are endocrine disrupting chemicals that are widely distributed in the aquatic environment. The aim of this study was to investigate the effects of TBT, TPT, and SnCl₂ on the embryonic development of zebrafish. In this study, zebrafish embryos were used to observe the acute toxicity of TBT, TPT, and SnCl₂. Fish embryo toxicity analysis was performed for different TBT, TPT, and SnCl₂ concentrations (1, 5, 10, 15, and 20 ng/L). Fertilized eggs in 24-well plates (20 eggs in each concentration) were incubated at 26°C for 4 days, and embryo clotting, embryo heartbeat, and morphological abnormalities were recorded after 96 h. Coagulation increased significantly in a dose-dependent manner, and TBT was able to induce coagulation in zebrafish embryos. Heartbeat changes significantly decreased (p < 0.05) in a dose-dependent manner at different TBT doses (p < 0.05). The percentage of mortality was higher in embryos at trace levels of TBT, indicating that the embryos are more sensitive to the toxicity of TBT. TBT is therefore extremely toxic and can have fatal consequences for zebrafish embryos, ultimately leading to the extinction of species and a decline in biodiversity in the aquatic environment. After analyzing the images 96 h after fertilization and converting them to a teratogenic index score, it was found that the index for the two compounds TPT and TBT was 4.6 and 9.6 ng/L, respectively.