Varied egg gas conductance, air cell gas tensions and development in Agapornis roseicollis

Different color varieties of the small African parrot, Agapornis roseicollis , lay eggs which differ by as much as a factor of 7 in gas conductance. Oxygen consumption (VO2) and air cell gas tensions (PAO2, PACO2) were measured repeatedly on individual eggs during development. No differences were observed in the ontogeny of VO2, incubation period, or hatchling mass of eggs with different gas conductances, in spite of large differences in PAO2 and PACO2. Low conductance eggs reached PAO2 as low as 46.0 torr (6.13 kPa) and PACO2 as high as 90.5 torr (12.07 kPa). Although pipping occurred earlier in low conductance eggs, pipping did not occur at similar air cell gas tensions in eggs differing in conductance. Chorioallantoic membrane development was about 75% complete on day 12 and not fully complete until day 18 of the 22-23 day incubation period. The capacity of avian embryos to develop and hatch normally in eggs of different conductances may be important in allowing adaptation to varying nesting environments.