During the internally pipped stage, there was a positive
relationship between V ·
O2lung and V ·
O2total with both variables
exhibiting a wide range. This positive relationship reflects the
fact that eggs were used at random times after internally
pipping. Embryos with lower V ·
O2lung are thought to have been
internally pipped and ventilating their lungs for relatively
shorter periods than embryos with higher V · O2lung. Comparisons
of the ratio ofV ·
O2lung toV ·
O2total between treatments suggest that
embryos were at similar stages of internal pipping in all
exposure groups (Table 1). Similar variability in the contribution
V ·
O2lung to V ·
O2total with respect to initiation of lung
ventilation has been observed by others in both internally and
externally pipped embryos (Menna and Mortola, 2002, 2003).
There is also a positive correlation between both VT and
breathing rate and V ·
O2total and V ·
O2lung (Menna and Mortola,
2002). Initially when an embryo begins to ventilate their lungs,
the lungs are filled with fluid (Vince and Tolhurst, 1975) and the
embryo must still rely heavily on the CAM forV · O2total. As they
continue to ventilate the lungs, the fluid dissipates and V ·
O2lung
increases. However, it is unknown how rapidly the fluid clears
from the lungs during this stage of hatching.