Japanese medaka exposed to gold nanoparticles: Only embryonic exposure generates irreversible hatching failure, developmental failure, and mortality of sac-fry

This study evaluated irreversible toxicity effects of gold nanoparticles (AuNPs) during the short-term (only embryonic stage) and long-term (both embryo and sac-fry stages) exposures of Japanese ricefish, Oryzias latipes (medaka) embryos and sac-fry. Embryos and sac-fry exposed to AuNPs at 8 and 15 days post-fertilization exhibited mortality, developmental failure, and abnormal appearance, and sac-fry additionally exhibited hatching failure and abnormal behavior. Embryos damaged by AuNPs during the embryonic stages failed to hatch and died, despite being raised under AuNP-free conditions after embryonic exposure. This study demonstrates that AuNPs have irreversible effects on O. latipes embryos and sac-fry, including the embryonic stages, regardless of the length of exposure. This result may be critical for predicting the potential continuous effects of AuNPs when the exposure duration of fish is short but includes the embryonic stages. To the best of our knowledge, this is the first study to test the toxicity of AuNP exposure on the embryos and sac-fry of O. latipes.