Anoxia-conditioning hormesis alters the relationship between irradiation doses for survival and sterility in the cactus moth, Cactoblastis cactorum (Lepidoptera: Pyralidae)

Authors: LOPEZ-MARTINEZ, GIANCARLO - University Of Florida; Carpenter, James; Hight, Stephen; HAHN, DANIEL - University Of Florida

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2015
Publication Date: 6/1/2016
Citation: Lopez-Martinez, G., Carpenter, J.E., Hight, S.D., Hahn, D.A. 2016. Anoxia-conditioning hormesis alters the relationship between irradiation doses for survival and sterility in the cactus moth, Cactoblastis cactorum (Lepidoptera: Pyralidae). Florida Entomologist. 99(spl):95-104. doi:10.1653/024.099.spl13.

Interpretive Summary: One of the most important components of a Sterile Insect Technique (SIT) program is appropriate irradiation dose. Knowing the dose-response for the target pest insect enables the selection of a dose that induces the highest level of sterility while preserving the sexual competitiveness and quality of the sterile insect. Finding this balance in Lepidoptera is crucial because of the use of inherited (F1) sterility, where the parent must be competitive enough to mate while the offspring must be sterile. Manipulations of atmospheric oxygen content have been shown to be an effective way of lowering unwanted side-effects of the radiation treatment while preserving sterility and improving sterile insect performance, particularly in fruit flies. In this study we tested the irradiation dose response of adults of the invasive cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), and the effects of those doses on sterility, longevity, and F1 performance, and whether a nitrogen conditioning-treatment (anoxia) prior to and during irradiation affected these metrics. We found that male and female fecundity was not impacted by dose or atmospheric treatment, but females were sterile at lower doses than males. Eggs of irradiated parents took longer to hatch than those of unirradiated controls, and offspring of moths irradiated in anoxia lived longer in the absence of food and water. Anoxia conditioning rescued female fertility at intermediate doses but had no effect on male fertility, which was always greater than female fertility at a given dose. Males generally lived longer than females and anoxia had a strong effect in lowering the male mortality rate and extending lifespan at a given dose. We show evidence that anoxia-conditioning prior to and during irradiation as part of a lepidopteran SIT program could improve parental and larval performance and longevity.

Technical Abstract: One of the most important components of a Sterile Insect Technique (SIT) program is appropriate irradiation dose. Knowing the organismal dose-response enables the selection of a dose that induces the highest level of sterility while preserving the sexual competitiveness and quality of the sterile insect. Finding this balance in Lepidoptera is crucial because of the use of inherited (F1) sterility, where the parent must be competitive enough to mate while the offspring must be sterile. Manipulations of atmospheric oxygen content have been shown to be an effective way of lowering post-irradiation somatic damage while preserving sterility and improving sterile insect performance, particularly in fruit flies. In this study we tested the irradiation dose response of adults of the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), and the effects of those doses on sterility, longevity, and F1 performance, and whether a nitrogen conditioning-treatment (anoxia) prior to and during irradiation affected these metrics. We found that male and female fecundity was not impacted by dose or atmospheric treatment, but females were sterile at lower doses than males. Eggs of irradiated parents took longer to hatch than those of unirradiated controls, and offspring of moths irradiated in anoxia lived longer in the absence of food and water. Anoxia conditioning rescued female fertility at intermediate doses but had no effect on male fertility, which was always greater than female fertility at a given dose. Males generally lived longer than females and anoxia had a strong effect in lowering the male mortality rate and extending lifespan at a given dose. We show evidence that anoxia-conditioning prior to and during irradiation as part of a lepidopteran SIT program could improve parental and larval performance and longevity. Keywords: sterile insect technique, dose response, invasive species, inherited (F1) sterility