Gas exchange and energy metabolism of the ostrich (Struthio camelus) embryo

We measured oxygen consumption (V-O2) and carbon dioxide emission (V-CO2) r ates, air-cell gas partial pressures of oxygen (PAO2) and CO2 (PACO2), eggs hell water vapour conductance and energy content of the ostrich (Struthio c amelus) egg, 'true hatchling' and residual yolk, and calculated RQ and tota l oxygen consumption (V-O2tot) for ostrich eggs incubated at 36.5 degreesC and 25% relative humidity. The V-O2 pattern showed a drop of approximately 5% before internal pipping. V-O2 just prior to internal pipping agrees with allometric calculations. Despite the higher incubation temperature compare d to other studies, and the resultant shorter incubation duration (42 days) , V-O2tot (91.71 kg(-1)) was similar to a previously reported value. RQ val ues during the second half of incubation (approx. 0.68) were lower than exp ected for lipid catabolism. Prior to internal pipping, PAO2 and PACO2 were 98 and 48.3 torr (13.1 and 6.4 kPa), respectively. The growth pattern of th e ostrich embryo is different from the typical precocial pattern, showing a time delay in the rapid growth phase. As a result, the lowered overall ene rgy expenditure for tissue maintenance, as compared to other species, is re flected in the low yolk utilization and high residual yolk fraction of the whole hatchling dry mass. These could also result from the relatively short incubation period of the ostrich egg, thereby evading desiccation by exces s water loss. (C) 2001 Elsevier Science Inc. All rights reserved.