Diapause is a fundamental component of the life cycle in the majority of insects living in environments characterized by strong seasonality. The present study addresses poorly understood associations and trade-offs between endogenous diapause duration, thermal sensitivity of development, energetic cost of development and cold tolerance. Diapause intensity, metabolic rate trajectories and lipid profiles of directly developing and diapausing animals were studied using pupae and adults of Pieris napi butterflies from a population in which endogenous diapause has been well studied. Endogenous diapause was terminated after 3 months and termination required chilling. Metabolic and post-diapause development rates increased with diapause duration, while the metabolic cost of post-diapause development decreased, indicating that once diapause is terminated, development proceeds at a low rate even at low temperature. Diapausing pupae had larger lipid stores than the directly developing pupae, and lipids constituted the primary energy source during diapause. However, during diapause, lipid stores did not decrease. Thus, despite lipid catabolism meeting the low energy costs of the diapausing pupae, primary lipid store utilization did not occur until the onset of growth and metamorphosis in spring. In line with this finding, diapausing pupae contained low amounts of mitochondria-derived cardiolipins, which suggests a low capacity for fatty acid β-oxidation. While ontogenic development had a large effect on lipid and fatty acid profiles, only small changes in these were seen during diapause. The data therefore indicate that the diapause lipidomic phenotype is developed early, when pupae are still at high temperature, and retained until post-diapause development.
The authors declare no competing or financial interests.
P.L., P.P., R.K., S.N., C.W.W., C.W. and K.G. designed the study. C.W. collected butterflies from the field. P.P., M.C., P.L. and K.G. set up the respirometry instrument. P.L., P.P. and D.P. performed the diapause intensity and metabolic rate experiments and R.K. and P.T. performed the lipidomic analyses. P.L. and K.G. did initial data analyses and wrote the first draft of the paper, and all authors contributed to the final version of the paper.
This work was funded by the Strategic Research Program Ekoklim at Stockholm University; the Knut and Alice Wallenberg Foundation (Knut och Alice Wallenbergs Stiftelse, KAW 2012.0058); and Vetenskapsrådet grants (VR-2012-3715 to S.N. and VR-2012-4001 to C.W.W.).
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.142687.supplemental
- Received May 2, 2016.
- Accepted July 18, 2016.
- © 2016. Published by The Company of Biologists Ltd