Abstract
It is generally assumed that light has no effect on the physiology of oocytes, zygotes, or early embryos. Therefore, little or no attention has been paid to lighting conditions during the handling of these cells in vitro. Here we show that cool white fluorescent light, rich in short-wavelength visible light and commonly used in research and clinical laboratories, produces more reactive oxygen species in mouse and hamster zygotes than does warm white fluorescent light. Mouse blastocysts that developed from zygotes shielded from light best developed to term fetuses followed by those exposed to warm white fluorescent light and then by those exposed to cool white fluorescent light. We hypothesized that light is one of the physical factors affecting embryonic environment and that its effects on cultured mammalian zygotes and embryos should not be overlooked.