The effects of oxygen partial pressure (PO 2) on development and respiration were investigated in the eggs of the Australian lungfish, Neoceratodus forsteri. At 20°C, embryonic survival and development was optimal at 15 and 20. 9 kPa. Development was slowed at 5 and 10 kPa and embryos did not survive 2 kPa. At lower PO 2, the rate of oxygen consumption also decreased. Embryos responded to hypoxia by hatching at an earlier age and stage of development, and hatching wet and dry gut-free masses were reduced. The role of oxygen conductance (GO 2) in gas exchange was also examined under selected environmental PO 2 and temperatures. The breakdown of the vitelline membrane changed capsule geometry, allowed water to be absorbed into the perivitelline space and increased capsule GO 2. This occurred at embryonic stage 32 under all treatments and was largely independent of both PO 2 and temperature (15, 20 and 25°C), demonstrating that capsule GO 2 cannot adaptively respond to altered environmental conditions. The membrane breakdown increased capsule diffusive GO 2 and stabilised perivitelline PO 2, but reduced the convective GO 2 of the perivitelline fluid, as the large perivitelline volume and inadequate convective current resulted in a PO 2 gradient within the egg prior to hatch.
|Number of pages||12|
|Journal||Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology|
|Publication status||Published - Oct 2011|
- Capsule conductance
- Neoceratodus forsteri