Effect of incubation temperature on oxygen consumption and ammonia production by Japanese medaka, Oryzias latipes, eggs and newly hatched larvae

To develop a database for use in designing sealed-container bioassays, oxygen consumption and ammonia production rates were compared for eggs and newly hatched larvae of Japanese medaka (Oryzias latipes). At 23, 26 and 29°C, the total amount of oxygen required to hatch an egg (49 to 54 μg O2.egg−1) was independent of temperature, but total oxygen required at 20°C (77 μg O2.egg−1) was significantly greater. Eggs produced no measurable ammonia (TAmm), but newly hatched larva produced 14 ng TAmm.h−1.larva−1 at 23°C and up to 48 ng TAmm.h−1.larva−1 at 29°C. When exposure to free air was denied, (a) oxygen, not ammonia, was the limiting factor for normal egg development, and (b) newly hatched larvae were unable to inflate their swimbladder.