ABSTRACT
Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that affect embryonic development. The purpose of this study was to examine the effects of embryonic exposure to PCBs on early retinal development in zebrafish, Danio rerio. Zebrafish embryos were immediately exposed to different concentrations (0, 0.125, 0.25, 0.5, 1.0 and 2.0โmg) of PCBs per liter of medium at 28.5โยฐC. Embryos were assessed at 30, 48, 72 and 96โh postโfertilization (hpf) for changes in embryonic survival rate, development, larval retinal morphology and ultrastructure of the retina. The results show that PCB exposure decreased the survival rate of embryos in a timeโ and doseโdependent manner. Embryos exposed to the higher concentrations of PCBs (0.5, 1.0 and 2.0โmgโl^โ1^) displayed obvious gross morphological deformities. At 72โhpf, the retinal layer development of zebrafish was delayed at higher PCB concentrations (1.0โmgโl^โ1^). At 96โhpf, irregularity of photoreceptor cells arrangement and thickening of photoreceptor and ganglionic layers were observed in PCBโtreated larvae at concentrations of 0.25โ1โmgโl^โ1^. Ultrastructural examination showed signs of growth inhibition of the photoreceptor outer segment at 0.25โ1โmgโl^โ1^ PCB exposure at 72โhpf, as well as the appearance of massive vacuoles and holes inside the outer segments in the PCB exposure group at 96โhpf. These results suggest that embryonic exposure to moderate and high levels of PCBs induced developmental deficits in zebrafish retinas, particularly in photoreceptor cells. Copyright ยฉ 2011 John Wiley & Sons, Ltd.