Lead and lead–arsenic combined exposure induces mortality and developmental impairments in zebrafish embryos: a study using wild-caught zebrafish from Bangladesh

Abstract

Heavy metal toxicity has become a global health burden, exerting various physiological effects on aquatic animals and humans. Zebrafish (Danio rerio) has emerged as a real-time model system for toxicological study. We previously reported the effects of arsenic on the embryonic development of zebrafish. The current study aimed to get deep insights into the toxic effects of another heavy metal, lead, on the early embryonic development of wild-caught zebrafish. We exposed freshly collected zebrafish embryos to different lead concentrations and studied different developmental and morphological changes using an inverted microscope. In a separate experiment, embryos were exposed to a combination of lead and arsenic to evaluate the combined effects of the elements. Lead concentration of as low as 0.25 mM resulted in developmental and morphological abnormalities in the zebrafish embryos. Exposure to different concentrations (0.25 mM, 0.5 mM, and 0.75 mM) caused a higher mortality rate of the embryos. Besides, an increased rate of arrested hatching, irregularities in size and shape of the yolk sac, deformed otic vesicle, and body curvature were observed in a dose-dependent manner. Lead exposure also resulted in reduced heart rate and severe pericardial edema. The combined effect of minimum concentrations of lead and arsenic that causes toxicity individually (0.25 mM and 1.0 mM, respectively) revealed a more severe effect than the individual treatments. This study's findings explain the association of heavy metal exposure with an increased rate of miscarriage/abortion incidences in highly polluted areas assisting in proper management and creating public awareness.