Effects of Hypoxia on Embryonic Development and Hatching in Two Ambystoma and Two Rana Species
The concentration of dissolved oxygen (DO) available to amphibian embryos fluctuates widely and is often quite low. I investigated the effects of low DO (hypoxia) on embryonic development and hatching of two Ambystoma and two Rana species. In Ambystoma, hypoxia resulted in slowed development, delayed hatching, and embryos that were less developed at the time of hatching. Although the levels of DO used were not lethal to embryos, temporary developmental abnormalities were observed and post-hatching survivorship decreased. Ambystoma eggs exposed to hypoxia increased dramatically in volume and surface area, presumably through influx of water. This response increased the diffusive conductance for oxygen. In contrast to Ambystoma, Rana embryos exposed to hypoxia hatched sooner than normoxic embryos. Hypoxia did not affect pre-hatching rate of development in Rana, presumably because hatching occurred at a very early stage of development. Overall, the results suggest that hypoxia has a negative effect on fitness for these species.
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