Metabolic reserves of diapausing western cherry fruit fly (Diptera: Tephritidae) pupae in relation to chill duration and post-chill rearing conditions

Authors: Neven, Lisa; Yee, Wee

Submitted to: Frontiers in Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2022
Publication Date: 9/16/2022
Citation: Neven, L.G., Yee, W.L. 2022. Metabolic reserves of diapausing western cherry fruit fly (Diptera: Tephritidae) pupae in relation to chill duration and post-chill rearing conditions. Frontiers in Insect Science. 2. Article 989673. https://doi.org/10.3389/finsc.2022.989673.
DOI: https://doi.org/10.3389/finsc.2022.989673

Interpretive Summary: A keystone in controlling insect pests is understanding the underlying physiology and phenology of the species. The Western cherry fruit fly, Rhagoletis indifferens is a serious pest of sweet cherries in the Pacific Northwest. Scientists at the USDA-ARS laboratory in Wapato Washington have worked to understand the key components of dormancy in this species. They measured the primary metabolic reserves of dormant pupae of western cherry fruit fly in relation to the duration of chilling and post-chilling warm temperature exposure. It was determined that dormant pupae utilize lipid (fat) reserves to support metabolism during this dormant state, and then more extensively to support post-dormancy development into flies. These results indicate the importance of fat reserves to the survival of dormant flies and may help understand the potential impact of climate change on single generation temperate fruit flies.

Technical Abstract: How different macronutrients are utilized at various stages of pupal diapause and the effects of winter length on nutrient reserves remain poorly studied for most insects. Western cherry fruit fly, Rhagoletis indifferens (Diptera: Tephritidae), is a specialist on cherries in higher latitudes or elevations in western North America that exhibits a rigid pupal diapause requiring chilling before adult development can occur. We determined the relationship between metabolic reserves and diapause status in R. indifferens pupae, testing the hypotheses that lipids are the primary reserves utilized during diapause and that long periods of warmth prior to chilling deplete these reserves more than periods of cold. Effects of 0- to 20-week durations at 3°C and subsequent exposure to 23°C and 16:8 L:D (warm rearing conditions) for 0 to 7 weeks on lipid, protein, carbohydrate, and glycogen reserves of R. indifferens pupae were determined. During diapause, lipid reserves were the primary source of energy utilized by R. indifferens, while protein and carbohydrate levels were stable throughout diapause and thus less utilized. At post-diapause, glycogen levels fluctuated the most, indicating that lipid reserves were converted to glycogen to support metabolism for adult fly development. Unchilled pupae did not deplete lipid reserves, unlike chilled pupae, likely because unchilled pupae remained in diapause. Rhagoletis indifferens have evolved a nutrient utilization strategy typical of rigid diapausing insects in higher latitude environments.