Effects of Cadmium and Zinc on the Gamete Viability, Fertilization, and Embryonic Development of Tripneustes gratilla (Linnaeus)

Heavy metals are frequently reported for their mutagenic and teratogenic effects on benthic organisms. Thus, this study aimed to determine the toxicity of cadmium (Cd) and zinc (Zn) in the gametes of T. gratilla and to compare its fertilization and embryonic development under the highest nongametotoxic concentrations of these heavy metals. Gamete viability of T. gratilla under CdCl(2) and ZnSO(4) treatments was assayed through resazurin reduction test (RRT) and was confirmed through gamete morphology assay. ZnSO(4) was more toxic to T. gratilla gametes than CdCl(2) and egg cells were more sensitive to both than the sperm cells. Higher concentrations of CdCl(2) and ZnSO(4) induced gamete apoptosis and necrosis while highest nongametotoxic concentrations were determined at 1 × 10(−3) M and 1 × 10(−4) M, respectively, and were used in an in vitro fertilization and embryonic development experiment. ZnSO(4) treatment inhibited fertilization more than CdCl(2) and yielded more deformed embryos, while both induced abnormalities and hindered further embryonic development. This study gives the first report on the specific concentrations of Cd and Zn that are toxic to T. gratilla gametes and has confirmed the teratogenic effects of these heavy metals.