Host fruits shape the changes in the gut microbiota and development of Bactrocera dorsalis (Diptera: Tephritidae) larvae

Bactrocera dorsalis infests a wide range of host fruits, some of which are suitable hosts, while others are less suitable ones. Although reports highlighted the bacteria-mediated adaptations to different host-fruits, the phenotypic cost and/or gain of the association between insect's gut bacteria and fruit substrates has not been fully studied. In this study, we hypothesized that, when the larvae are confronted with host fruits with different suitability, its community structure changes over time as a result of its adaptation. To support this, a single female fruit fly was allowed to lay eggs on five different host fruits, then we monitored the larval development parameters and analyzed the gut bacterial communities of larvae fed apple and banana at first (F-1) and fifth (F-5) generations. The larval developmental parameters (length and dry weight) did not vary significantly across generations, but the developmental duration was greatly affected by fruit types and larval stages. The larval development time was extended considerably in apple and tomato, but shortened in banana and mango. Insects grown in apple and banana have similar bacterial phylotypes to those of the parental female at F-1 (predominance of Proteobacteria). However, at F-5, the proportions of Firmicutes, Bacteroidetes, Actinobacteria, Verrucomicrobia and Cyanobacteria increased substantially in larvae grown in apple, compared to banana. These findings confirm our hypothesis and suggest that, gut bacteria and host fruits are intimately tied in predicting B. dorsalis larval development, important data for bacteria-based control of this pest.