ABSTRACT: The ability of an organism to cope with environmental stressors varies across the life span because of developmental stage-specific responses and age-related functional declines. In the present study, we examined the effect of age on acute copper toxicity in Japanese medaka (Oryzias latipes). We first determined the median lethal concentration (LC50) at 96 h for embryos, 7-day-old fry, and 6-month-old medaka. Embryos were exposed to 0, 15, 30, 60, 125, 250, and 500 ppb CuSO4 through hatching. Fry were exposed to 0, 20, 50, 75, 100, 150, 250, and 500 ppb CuSO4 for 96 h. Adult fish were exposed to 0, 100, 150, 200, 250, and 300 ppb CuSO4 for 96 h. The 96-h LC50 was 804 ppb for embryos, 262 ppb for embryonically exposed larvae, 60.3 ppb for 7-day-old fry, and
