Effects and implications of antibiotic treatment on Wolbachia-infected vine weevil (Coleoptera: Curculionidae)

1. The parthenogenetic weevil Otiorhynchus sulcatus was collected from five geographical locations in the U.S.A. All weevils from each location were infected by Wolbachia belonging to supergroup B. 2. We hypothesized that treatment with tetracycline, which has been used to clear Wolbachia infection, would influence the reproduction of Wolbachia-infected parthenogenetic O. sulcatus females. Tetracycline treatment of preovipositional O. sulcatus females specifically inhibited egg hatching but had no effect relative to controls on any other physiological trait. 3. Treatment with gentamicin, which reportedly has no effect on Wolbachia infection but is indistinguishable from tetracycline in inhibiting protein synthesis of other bacterial genera, did not influence egg hatching. 4. These findings strongly suggest that the inhibition of egg development results from the antibiotic effect on Wolbachia rather than by direct toxic effects on O. sulcatus physiology. 5. We speculate that Wolbachia may be necessary for normal development of O. sulcatus eggs and discuss the implications of these findings for O. sulcatus ecology.