Transinfected Wolbachia have minimal effects on male reproductive success in Aedes aegypti

Abstract

Background: Wolbachia are maternally inherited endosymbiotic bacteria that manipulate the reproductive success of their insect hosts. Uninfected females that mate with Wolbachia infected males do not reproduce due to cytoplasmic incompatibility (CI). CI results in the increased frequency of Wolbachia-infected individuals in populations. Recently, two Wolbachia strains, the benign wMel and virulent wMelPop have been artificially transinfected into the primary vector of dengue virus, the mosquito Ae. aegypti where they have formed stable infections. These Wolbachia infections are being developed for a biological control strategy against dengue virus transmission. While the effects of Wolbachia on female Ae. aegypti have been examined the effects on males are less well characterised. Here we ascertain and compare the effects of the two strains on male fitness in resource-limited environments that may better approximate the natural environment.

Methods: A series of population mating trials were conducted to examine the effect of Wolbachia infection status (with strains wMel and wMelPop) and male larval nutrition on insemination frequency, remating rates, the fecundity of females, the hatch rates of eggs and the wing length and fertility of males.

Results: wMel and wMelPop infections reduce the fecundity of infected females and wMelPop reduces the viability of eggs. Low nutrition diets for males in the larval phase affects the fecundity of wMel-infected females. Neither strain of Wolbachia affected sperm quality or viability or the ability of males to successfully mate multiple females.

Conclusions: The benign strain of Wolbachia, wMel causes similar reductions in fecundity as the more virulent, wMelPop, and neither are too great that they should not still spread given the action of CI. The ability of Wolbachia-infected males to repeat mate as frequently as wildtype mosquitoes indicates that they will be very good agents of delivering CI in field release populations.

Figure 1

Egg viability expressed as median hatch rate ± quartiles. Kolmogorov-Smirnov test is significant if *P < Holm-Bonferroni α (Table 3). The wMelPop strain in female Ae. aegypti (A.PGYP1.out) reduced the hatch rates of eggs.

Figure 2

Mean fecundity ± SEM. Significant difference between lines *P < Holm-Bonferroni α. Both the wMel (MGYP2.out) and wMelPop (A.PGYP1.out) strains of Wolbachia reduced the fecundity of infected Ae. aegypti.