The energetics of endotrophic development in the frog Geocrinia vitellina (Anura : Myobatrachinae)

The energetics of endotrophic development, where the nutrition required to complete metamorphosis is provided solely by yolk, has seldom been quantifi ed. The energy cost of development to metamorphosis of the endotrophic Aust ralian frog Geocrinia vitellina was measured using bomb calorimetry and clo sed-system respirometry. Dry yolk had an energy density of 26.4 J mg(-1), a nd an average 2.8-mm-diameter ovum contained 144 J. Incubation at 15 degree sC produced a froglet of 5.8 mm snout-vent length, containing 88 J in 87 d, with 11% of residual yolk in the gut, which is markedly less than the 50% recorded in another endotroph, Eleutherodactylus coqui. Geocrinia vitellina lost 56 J of metabolic energy during development to metamorphosis at 15 de greesC, and the total production efficiency was 61.0%. A review of publishe d egg energy densities found a mean for amphibians of 25.1 kJ g(-1), signif icantly lower than the mean of 27.1 kJ g(-1) for reptiles. Moreover, availa ble amphibian data suggest that endotrophic species have high yolk energy d ensities and low mass-specific rates of oxygen consumption relative to exot rophic species (with feeding larvae); consequently, large ovum size may not necessarily be prerequisite for endotrophic development.