Developmental Changes in Metabolic Intensity between Flying and Non-Flying Insects
Metabolic scaling is an extremely important aspect of life. Animals must intake and expend different levels of energy to survive depending on their body size and activity levels. The basal metabolic rate refers to the base rate of energy needed for an organism to live. Smaller animals have higher basal metabolic rates than larger ones due to their higher surface area to volume ratio. Flight activity is not included in the scheme of a basal metabolic rate but an organism capable of flight is likely to have a higher basal metabolic rate because of the high energetic costs of flight (Suarez, 2000). Thus, to understand the base changes required to the metabolic rate required for flight, we investigated the differences therein between the larval and adult stages of an invertebrate which changes into one capable of flight, Hermetia illucens, and one which remains incapable of flight between life stages, Tenebrio molitor. Using respirometry, we calculated the oxygen consumption of each specimen during a period of rest in the larval and the adult stage. The oxygen consumption was then converted to a metabolic intensity and basal metabolic rate. We determined that both species had lower metabolic intensity as adults compared to their larval intensities. During development, T. molitor had a much larger drop in metabolic intensity than H. illucens. We provide evidence, first, that the metabolic demands of flight correlate with higher metabolic intensity than in stationary species and, second, that in stationary species, larval metabolic demands are greater than in the adult stage.