The Roles of Temperature and Dissolved Oxygen in Microhabitat Selection by the Tadpoles of a Frog (Rana pipiens) and a Toad (Bufo terrestris)

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Abstract
Dissolved O2 and temperature data from habitats frequented by the tadpoles of R. pipiens and B. terrestris are related to laboratory studies of rates of O2 consumption (.ovrhdot.VO2), Q10, critical O2 tensions (Pc) and critical thermal maxima (CTM). Both species were acclimated to 22, 27 and 32 C for studies of physiological parameters. CTM was higher for both species in the earlier stages of development, and was higher in Bufo than in Rana at all temperatures. .ovrhdot.VO2 was higher in Bufo tadpoles than in Rana. The Pc increased with temperature in all stages of Bufo, but only in the younger stages of Rana. Field studies showed that Bufo tadpoles were found in warmer, more highly oxygenated microenvironments than were Rana tadpoles. Shallow-water breeders, such as Bufo, probably emphasize adaptations to high temperatures; permanent-water forms, such as Rana, emphasize adaptations to variations in O2 availability.