Abstract
To examine how nutritional quality and resident gut bacteria interplay in improving the fitness of an oligophagous fruit fly, Bactrocera minax, artificial sucrose diets and full diets (sucrose, tryptone and yeast extract) were fed to flies with and without antibiotic supplementation. Furthermore, Klebsiella oxytoca and Citrobacter freundii were supplemented to sucrose-only diets. Flies were maintained in the laboratory and the fitness parameters, male and female longevity, number of copulations and female fecundity, were recorded. Full diet without bacterial depletion significantly increased fecundity and copulation. In the absence of gut bacteria, flies fed with full diets had significantly decreased mean fecundity and copulation rate. Flies that were fed with sucrose diet had a very low copulation rate and produced no eggs. Diet type and the presence of bacteria did not have any effect on the average longevity of male and female flies. Bacterial supplementation in sucrose diets did not improve any of the measured parameters. The results demonstrate that gut bacteria interact with diet to influence mating and reproduction in B. minax. Symbiotic bacteria significantly and positively impact reproduction in B. minax; however, their impact can only be fully realized when the flies are fed with a nutritionally complete diet.
Highlights
Many insect species are able to survive and reproduce despite feeding on what are nutritionally poor diets
We further investigated if specific bacteria isolates could improve on the low nutritional quality of sugar diets
Quantification of bacterial knock-down was not directly estimated after antibiotic treatment, its effect on fitness was seen in the results
Summary
Many insect species are able to survive and reproduce despite feeding on what are nutritionally poor diets. Aphids live on plant sap which is of low nutritional quality [1], while termites live on a non-degradable cellulose diet [2]. That these organisms, and numerous other examples, are nutritionally successful is considered to be the result of diet modification by symbiotic bacteria that these insects harbour [3]. The symbiont and its host insect have developed a very intimate relationship, where they depend primarily on each other for nutrition [1]. The role symbiotic bacteria play in nutrition is less apparent, except when the host insect is nutritionally stressed. No significant differences were observed when both groups were reared on a standard diet [10]
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