Embryotoxic and teratogenic effects of polyethylene microbeads using the zebrafish Danio rerio (Hamilton, 1822)

Abstract

Background: The escape of polyethylene microbeads from waste-water treatment facilities to aquatic habitats has been a major concern by scientific communities due to the adverse effects on aquatic organisms as well as the well-being of the marine and terrestrial ecosystems.

Objective: This study was conducted to evaluate the embryotoxic and teratogenic effects of polyethylene microbeads on the early development of the zebrafish Danio rerio using the Fish Embryo Acute Toxicity Test (FET).

Methodology: Sixty (60) zebrafish embryos were exposed to polyethylene microbead suspensions (PE-MBS) of 20 μg/L, 200 μg/L, and 2000 μg/L concentrations. Using FET, the toxicological endpoints (i.e., egg coagulation, lack of somite formation, non-detachment of tail, and lack of heartbeat) were observed every 24 hours until the 96th-hour exposure. Hatching of the embryo from the chorion was observed from 48-96 hpf (hours-post fertilization), and at least four parameters of teratogenicity (i.e., edema of the pericardium and yolk sac, bent axis, tail curvature, and collapsed swim bladder) was observed at 144 hpf.

Results: Significant differences between means and variances in the embryotoxic and teratogenic effects were observed for all treatment groups in relation to the negative control (reconstituted water). The emulsifier control (0.01% Tween 80, p-value=0.9), the solvent control (1% DMSO, p-value = 0.9), and the 20 μg/L PE-MBS (p-value = 0.92) did not significantly differ with the negative control group. However, the positive control (5% ethanol, pvalue= 7.8) and 200 μg/L (p-value = 1.1), and 2000 μg/L (p-value = 1.48) of PE-MBS were significantly embryotoxic and teratogenic to the developing organism.

Conclusion: The high concentrations of PE-MBS (200 μg/L and 2000 μg/L) may induce early hatching, mortality, and malformations. Tukey Kramer post hoc test substantiated that PE-MBS toxicity is dose-dependent since embryotoxicity and teratogenicity increase at higher concentrations. Further studies should be conducted to know more about the adverse effects of polyethylene microbeads on the development, physiology, and genomics of freshwater fishes.