METABOLIC COST OF DEVELOPMENT IN TERRESTRIAL FROG EGGS (PSEUDOPHRYNE-BIBRONII)

We incubated Pseudophryne bibronii eggs at selected T(a) (7-degrees, 12-degrees, 17-degrees, 22-degrees-C) and substrate water potentials (0 and -25 kPa) to determine their effects on rate of O2 consumption (VO2) of the embryos, incubation time, growth rate, and differentiation rate. Incubation to median hatching stage (stage 27) increased from 17 d at 22-degrees-C to about 140 at 7-degrees-C, and VO2 increased in proportion to age at all temperatures. At 0 kPa water potential, the total O2 consumed until hatching stage decreased from about 1.2 mL at 7-degrees-C, to 0.81 mL at 12-degrees-C, to a low of 0.58 mL at 17-degrees-C, and increased slightly to 0.67 mL at 22-degrees-C. However, gut-free dry mass of 12-degrees-C hatchings was significantly higher then those at 17-degrees and 22-degrees-C, so the energy cost of producing 1 mg of dry, gut-free embryo was similar (0.47-0.55 mL/mg) between 12-degrees and 22-degrees-C. Incubation at lower water potential (-25 kPa) reduced VO2 by 19%-28% and retarded growth rate but did not affect differentiation rate or incubation time.