Abstract: 【Aim】 This study aims to investigate the oviposition selection of Drosophila melanogaster to aerobic and anaerobic metabolites of Lactobacillus brevis, and to elucidate the underlying mechanism and biological significance of their effects on Drosophila oviposition behavior. 【Methods】 The oviposition preference of female adults of D. melanogaster was assayed by using the two-choice apparatus. The sensory modality that mediates this behavior was studied by using dark conditions, olfactory mutants and flies with forelegs surgically removed. The developmental duration and survival rate of offspring were determined to evaluate the biological significance of the oviposition avoidance to lactic acid. The intestinal epithelial cell proliferation was observed by immunofluorescence. 【Results】 The female adults of D. melanogaster avoided laying eggs on food covered with metabolites of L. brevis by anaerobic fermentation, with the oviposition index of -0.47. The concentration of the metabolite lactic acid was 0.4 mmol/L under the aerobic condition, while it was 126.8 mmol/L under the anaerobic condition. Female adults of D. melanogaster avoided laying eggs on the food with lactic acid, and the oviposition index decreased with lactic acid in a dosage dependent manner. D. melanogaster had obvious oviposition avoidance to lactic acid. The oviposition avoidance response was impaired in the flies with forelegs surgically removed. The time to puparium formation and to adult emergence of the larvae on the food with 70 mmol/L lactic acid was prolonged by 1.42 d and 1.17 d, respectively, and the larval survival rate decreased by 36.0%, as compared to those of the control. Lactic acid induced intestinal dysplasia with the increased number of mitotic cells. 【Conclusion】 Female adults of D. melanogaster avoid laying eggs on the food covered with metabolites of L. brevis by anaerobic fermentation. The metabolite lactic acid produced under anaerobic condition, which is detected by flies mainly through taste perception, induces the oviposition avoidance of D. melanogaster, thus promoting the development and the survival rate of their progeny.

Key words: Drosophila melanogaster, Lactobacillus brevis, lactic acid, oviposition behavior, gustatory system, developmental duration, survival rate