Comparative Toxicity Of Lead And Cadimium On Developing Zebrafish Embryos

Abstract

This study investigated the effects of lead (Pb²⁺) and cadmium (Cd²⁺) on zebrafish (Danio rerio) embryos by assessing survival rates and cardiac development. Embryos were exposed to five concentrations of each metal (0.1, 1, 10, 20, and 100 µg/L). Results demonstrated that the toxicity of both metals was strongly time- and dose-dependent. At environmental concentrations (0.1 - 1 µg/L), the impact on survival was negligible within the first 48 hours but became apparent after 72 hours and was particularly severe at the 168-hour larval stage, where survival rates plummeted to below 7% at concentrations ≥10 µg/L. Cadmium showed a slightly higher toxicity trend than lead in this aspect. Regarding cardiac activity, both metals induced dose-dependent tachycardia (increased heart rate), with lead exerting a more potent stimulatory effect than cadmium. Notably, alterations in heart rate were detectable as early as 48 hours post-exposure, establishing this parameter as a sensitive early indicator of toxicity. The study affirms that both lead and cadmium pose significant threats to embryo survival and physiological health, highlighting the critical need for monitoring heavy metal contamination to protect aquatic ecosystems and aquaculture practices.