Abstract
The Mediterranean fruit fly (medfly), Ceratitis capitata, is a pest of worldwide substantial economic importance, as well as a Tephritidae model for sterile insect technique (SIT) applications. The latter is partially due to the development and utilization of genetic sexing strains (GSS) for this species, such as the Vienna 8 strain, which is currently used in mass rearing facilities worldwide. Improving the performance of such a strain both in mass rearing facilities and in the field could significantly enhance the efficacy of SIT and reduce operational costs. Recent studies have suggested that the manipulation of gut symbionts can have a significant positive effect on the overall fitness of insect strains. We used culture-based approaches to isolate and characterize gut-associated bacterial species of the Vienna 8 strain under mass rearing conditions. We also exploited one of the isolated bacterial species, Enterobacter sp., as dietary supplement (probiotic) to the larval diet, and we assessed its effects on fitness parameters under the standard operating procedures used in SIT operational programs. Probiotic application of Enterobacter sp. resulted in improvement of both pupal and adult productivity, as well as reduced rearing duration, particularly for males, without affecting pupal weight, sex ratio, male mating competitiveness, flight ability and longevity under starvation.
Highlights
Symbiosis is a for a long time underestimated interaction that is ubiquitous in the animal kingdom and in insects [1,2,3]
Its effects were assessed with respect to rearing efficiency and biological quality of Vienna 8 genetic sexing strains (GSS), a medfly strain used for sterile insect technique (SIT) applications worldwide, according to standard quality control parameters used in mass rearing facilities and SIT operational programs [38]
The results can be summarized as follows: (a) a culture-dependent approach, using larval and adult guts resulted in the isolation of three bacterial species (Providencia sp., Enterobacter sp., and Acinetobacter sp.); (b) larval diet-based probiotic application of Enterobacter sp., in particular as “live bacteria”, resulted in improved pupal and adult productivity, as well as faster development, of males and (c) there was no effect on weight, sex ratio, male mating competitiveness, flight ability or longevity under stress
Summary
Symbiosis is a for a long time underestimated interaction that is ubiquitous in the animal kingdom and in insects [1,2,3]. SIT refers nearly always to the mass-rearing and release of irradiation-induced sterile flies in the field, targeting wild populations of the species [14]. These releases lead to sterile crosses and subsequently to population suppression. Genetic Sexing Strains (GSSs), which conditionally produce only males, have been developed for medfly (such as the Vienna 7 and Vienna 8 GSSs); they are currently being used in mass rearing facilities and large scale operational SIT programs on almost every continent [15]. Factors affecting the rearing efficiency and the biological quality of produced insects may include the colonization and laboratory adaptation processes of the strains used, the mass rearing conditions, the sterilization through irradiation, and pre-release and release handling [14]
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