Excess Sucrose in the Larval Diet Alters Gut Microbiota and Reduces Body Size and Longevity of Bactrocera dorsalis (Hendel).

The oriental fruit fly is a global invasive pest that damages a wide range of fruits and vegetables. The sucrose content of host plants consumed during the larval stage has important influence on adult phenotypic traits. In this study, three sucrose concentration levels were established in the larval artificial diet to examine their effects on adult phenotypic traits and gut microbiota. The results showed that low-sucrose diet (3% (w/w)) led to a significant increase in the pupa length by 3.5% and weight by 27.7% compared to individuals from the control, whereas high-sucrose diet (22% (w/w)) resulted in a notable decrease in the pupa length by 4.2% and weight by 15.0% compared to individuals from the control. Moreover, low-sucrose diet led to larger ovaries and longer lifespans of adult flies compared to those in the control. For the composition of gut microbiota, 26 bacteria groups were significantly enriched in the LSD group, and 17 bacteria groups were significantly enriched in the HSD group. Our study demonstrates that dietary sucrose concentration has influence on biological traits in Bactrocera dorsalis, potentially in association with variation in gut microbiota composition, and provides a foundation for future investigations into host adaptation in this species.