Evaluating impacts of radiation-induced sterilization on the performance and gut microbiome of mass-reared Mediterranean fruit fly (Ceratitis capitata) in Hawai’i

Authors: Mason, Charles

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2024
Publication Date: 8/9/2024
Citation: Mason, C.J. 2024. Evaluating impacts of radiation-induced sterilization on the performance and gut microbiome of mass-reared Mediterranean fruit fly (Ceratitis capitata) in Hawai’i. Journal of Economic Entomology. Article toae173. https://doi.org/10.1093/jee/toae173.
DOI: https://doi.org/10.1093/jee/toae173

Interpretive Summary: Sterile insect technique (SIT) is a useful strategy for mitigating establishment of invasive insect species. SIT of the pest tephritid Mediterranean fruit fly (medfly), Ceratitis capitata, has been effective in preventing establishment in vulnerable agricultural regions of the United States. In order to improve the efficacy of SIT through use of microbial manipulation, the goal of this study was to evaluate performance parameters and the gut microbiome of flies. To identify baseline performance metrics on the effects of irradiation on the gut microbiome of mass-reared flies in Hawaii, I performed a study across multiple timepoints where I assessed fly performance metrics and microbiome (bacterial 16S-rRNA) variation in medfly. Irradiated flies performed poorly compared to non-irradiated flies. However, I did not observe any differences in the gut microbiome of the flies assessed in this study. Samples were dominated Klebsiella, a common gut bacterial symbiont in pest tephritid fruit flies. This work contrasts with other research demonstrating the effects of irradiation on gut microbiota of flies.

Technical Abstract: Sterile insect technique (SIT) is a useful strategy for mitigating establishment of invasive insect species. SIT of the pest tephritid Mediterranean fruit fly (medfly), Ceratitis capitata, has been effective in preventing population establishment in vulnerable agricultural areas of the United States. However, irradiation-induced sterilization of males mass-reared for SIT releases can cause detrimental impacts, resulting in reduced mating performance. Additionally, medfly reared for SIT have been shown to have differences in their microbiomes relative to other population sources, whcih has been postulated to be a factor in the how well flies compete with wild conspecifics. To identify baseline performance metrics on the effects of irradiation on the gut microbiome of mass-reared flies in Hawai’i, I performed a study across multiple timepoints where I assessed fly performance metrics and microbiome (bacterial 16S-rRNA) variation in medfly. Medfly were selected from mass-reared trays intended for release, and paired samples were either irradiated or left as controls and transported to the laboratory for evaluation. Irradiated flies exhibited fewer successful fliers, more rapid mortality rates, and were less active relative to control, non-irradiated flies. Contrary to initial expectations, irradiation did not have strong impacts on the composition or diversity of bacterial reads. Samples were primarily comprised of sequences classified as Klebsiella and there were low levels of both read and taxonomic diversity relative to other 16S surveys of medfly. Although this study does not demonstrate a strong effect of irradiation alone on the medfly microbiome, there are several explanations for this discrepancy that I address.