title: Effects of environmental oxygen on development and respiration of Australian lungfish (Neoceratodus forsteri) embryos.
abstract: The effects of oxygen partial pressure ([Formula: see text]) 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 [Formula: see text], 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 ([Formula: see text]) in gas exchange was also examined under selected environmental [Formula: see text] and temperatures. The breakdown of the vitelline membrane changed capsule geometry, allowed water to be absorbed into the perivitelline space and increased capsule [Formula: see text]. This occurred at embryonic stage 32 under all treatments and was largely independent of both [Formula: see text] and temperature (15, 20 and 25°C), demonstrating that capsule [Formula: see text] cannot adaptively respond to altered environmental conditions. The membrane breakdown increased capsule diffusive [Formula: see text] and stabilised perivitelline [Formula: see text], but reduced the convective [Formula: see text] of the perivitelline fluid, as the large perivitelline volume and inadequate convective current resulted in a [Formula: see text] gradient within the egg prior to hatch.
authors: Ecology and Evolutionary Biology, University of Adelaide, Adelaide, SA, 5005, Australia. casey.mueller@adelaide.edu.au
authors: Casey A
authors: CA
authors: Mueller
authors: Jean M P
authors: JM
authors: Joss
authors: Roger S
authors: RS
authors: Seymour
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000502:physiology*; D004781:Environmental Exposure; D005399:Fishes / Q000196:embryology / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D012119:Respiration
chemical_list: D010100:Oxygen