Meeting Abstract
Flight is an energetically demanding activity, which may require a remodeling of metabolic pathways to support higher aerobic scope. This is likely to be a component setting the costs of flight for wing-polymorphic species. Adult wing-polymorphic crickets (Gryllus firmus) specialize either in dispersal (LW) or reproduction (SW) due to a resource-based trade-off between flight and ovary synthesis. We hypothesize that the LW morph has higher tissue-specific mitochondrial activity and hence higher whole-organism respiration to support flight compared to the SW morph. Using a treadmill respirometer, we measured resting metabolic rate (RMR), maximal metabolic rate (MMR), and locomotor performance. LW morphs had greater endurance than SWs as they ran for longer and reached higher speeds prior to exhaustion. This was accompanied by a higher mass-specific MMR but similar RMR compared to the SW morph, reflecting a larger aerobic scope for the LW morph. Tissue-specific mitochondrial activity was determined for jumping-leg muscle, dorsoventral flight muscle, and fat body and correlated to the aerobic performance of the same individuals. Higher MMRs were found to be positively correlated with higher citrate synthase activity in LW fat body but not in leg or flight muscle. Fat body plays an important role in lipid synthesis, storage, and mobilization and this work suggests that it is also important for meeting the energy demands of dispersal in LW crickets. Combined, the higher tissue-specific activity in fat body and aerobic capacity in the LW morph presumably support dispersal through flight. Overall, our study provides a novel perspective on how processes at the organ- and tissue-level can constrain whole-organismal performance.
