Sex differences in metabolic rate (MR) can result from dimorphism in the performance of energetically demanding activities. Male crickets (Teleogryllus oceanicus) engage in costly calling and aggressive activity not performed by females. Consistent with this difference, we found higher maximal MR, factorial scope, and fat content in males than females. T. oceanicus song is also costly because it attracts the parasitoid fly Ormia ochracea. Parasitized crickets had reduced maximal MR consistent with a metabolic cost to harboring larvae. This cost was greater for females, either because females invest more heavily into reproduction at the expense of metabolic capacity, or because males are under stronger selection to respond to infection. Little is known about O. ochracea outside of its auditory system and parasitic lifestyle. We observed greater resting MR in male flies, possibly reflecting a sex difference in the requirement for metabolic power output, because male flies perform potentially costly mating behavior not seen in females. We found a positive relationship between larval density within a cricket and pupal resting MR, suggesting that crickets in good condition are able to both harbor more larvae and produce larvae with higher resting MR. These results reveal a complex interplay between the metabolism of crickets and their fly parasitoids.
|Number of pages
|Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
|Published - Nov 2004
Bibliographical noteFunding Information:
Acknowledgements We are grateful to J.T. Rotenberry for assistance with field measurements, L.P. Nunney, D. Price and D.N. Reznick for allowing us to use their laboratory facilities, and the University of Hawaii, Hilo groundskeeping staff for their assistance in the field. This research was supported by the University of California at Riverside Intramural Funds to M.A.C. M.Z. is supported by grants from the US National Science Foundation and the UCR Academic Senate. The experiments comply with the current laws of the USA.
- Field cricket
- Metabolic rate
- Parasitoid fly
- Pupal metabolism
- Sexual dimorphism