Energetics of metamorphosis in two holometabolous insect species:Manduca sexta (Lepidoptera: Sphingidae) andTenebrio molitor (Coleoptera: Tenebrionidae)

Gas-exchange rates (VO2 and VCO2) measured from intact Manduca sexta and Tenebrio molitor pupae throughout metamorphosis decrease immediately following pupation, then increase during the last 60% of pupal development. Metabolic rates and rate of development increased with temperature between 22°C and 32°C in both species. There was, however, no significant effect of temperature on cumulative oxygen consumption over the duration of metamorphosis for either species. Although M. sexta pupae are 10 times as large as T. molitor pupae, their mass-specific cost of metamorphosis (per gram of pharate adult) was similar to that of T. molitor. The large-scale histolysis and subsequent remodeling of tissues during metamorphosis makes it difficult to quantify the mass of metabolically active tissue in pupae. A mitochondrial index (MI) related to mitochondrial membrane surface area was calculated using rhodamine-123-labeled mitochondria from M. sexta pupae, yielding a measure of pupa oxidative capacity and, indirectly, the amount of active tissue in the pupa. Across development, MI fluctuated in a manner resembling VO2 curves from intact M. sexta. Although both MI and VO2 increased during the latter half of development, the increase in MI began earlier and was proportionally larger than the observed increase in VO2. This suggests that, through most of metamorphosis, M. sexta pupae probably have a substantial aerobic potential that remains unutilized until emergence of the adult moth. J. Exp. Zool. 280:344–353, 1998. © 1998 Wiley-Liss, Inc.