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

Abstract

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 ofT. gratillaand to compare its fertilization and embryonic development under the highest nongametotoxic concentrations of these heavy metals. Gamete viability ofT. gratillaunder CdCl2and ZnSO4treatments was assayed through resazurin reduction test (RRT) and was confirmed through gamete morphology assay. ZnSO4was more toxic toT. gratillagametes than CdCl2and egg cells were more sensitive to both than the sperm cells. Higher concentrations of CdCl2and ZnSO4induced 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 anin vitrofertilization and embryonic development experiment. ZnSO4treatment inhibited fertilization more than CdCl2and 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 toT. gratillagametes and has confirmed the teratogenic effects of these heavy metals.