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.