Fig. 4. Time required for red-eyed treefrog embryos to reposition gills or head near air-exposed egg surface after experimental manipulation turning animals to face hypoxic rear of egg, and time until the next movement for controls manipulated similarly but positioned facing air-exposed egg surface. Embryos were watched until they moved or for 120 s (2 days old) or 60 s (3 days old). Many control embryos did not move; time watched was used as time to move for these animals. Data are means ± s.e.m.; N=25 embryos per treatment per age.