Effect of nickel on embryo development and expression of metallothionein gene in the sea urchin (hemicentrotus pulcherrimus)

Sea urchin embryo has been used to monitor pollutants in marine environments. Nickel (Nickel chloride, Ni), as a heavy metal, is a chemical element with the chemical formula NiCl₂-OH₂O. It may cause harmful effects on the central nervous system and growth. Metallothionein (MT) is a metal binding protein and it play a regulatory role in the homeostasis and detoxification of heavy metals. In this study, we examined the gametotoxic and embryotoxic effects of Ni at various concentrations (O, 10, 25, 50, 100, 500 ppb) in the sea urchin Hemicentrotus pulcherrimus. Spawning was induced by injecting 1 ml of 0.5 M KCl into coelomic cavity. Experiment was begun within 30 min the collection of both gametes. The fertilization and embryo development rates test were performed for 10 min and 64 h after fertilization, respectively. Results of this study, the fertilization rates in the control condition (not including Ni) and experimental group were not significantly changed. However, the embryo development rates were significantly decreased with concentration dependent manner. Especially, 50 ppb Ni treatment was significantly lower than vehicle control at 64 h onward. The normal embryogenesis rate was significantly inhibited in exposed to Ni (ECa,=34.19 ppb, 95% 01=29.56-38.09 ppb). The NOEC and LOEC of normal embryogenesis rate were <10 ppb and 25 ppb, respectively. The expression of MT mRNA gene was significantly increased with concentration dependent manner. These results suggest that the early embryo stages oí H. pulcherrimus have toxic effect at greater than 25 ppb of Ni concentration and MT mRNA gene may be used as a biomarker gene for risk assessment on contamination of Ni.