Antibiotic treatment leads to the elimination of Wolbachia endosymbionts and sterility in the diplodiploid collembolan Folsomia candida

<p>Abstract</p> <p>Background</p> <p><it>Wolbachia </it>is an extremely widespread bacterial endosymbiont of arthropods and nematodes that causes a variety of reproductive peculiarities. Parthenogenesis is one such peculiarity but it has been hypothesised that this phenomenon may be functionally restricted to organisms that employ haplodiploid sex determination. Using two antibiotics, tetracycline and rifampicin, we attempted to eliminate <it>Wolbachia </it>from the diplodiploid host <it>Folsomia candida</it>, a species of springtail which is a widely used study organism.</p> <p>Results</p> <p>Molecular assays confirmed that elimination of <it>Wolbachia </it>was successfully achieved through continuous exposure of populations (over two generations and several weeks) to rifampicin administered as 2.7% dry weight of their yeast food source. The consequence of this elimination was total sterility of all individuals, despite the continuation of normal egg production.</p> <p>Conclusion</p> <p>Microbial endosymbionts play an obligatory role in the reproduction of their diplodiploid host, most likely one in which the parthenogenetic process is facilitated by <it>Wolbachia</it>. A hitherto unknown level of host-parasite interdependence is thus recorded.</p

Wolbachia endosymbiont is essential for egg hatching in a parthenogenetic arthropod.

Wolbachia pipientis can induce a range of sex ratio distortions including parthenogenesis. Recently Wolbachia has been detected in the diploid, parthenogenetic, collembolan species Folsomia candida. In this paper we address the effect of Wolbachia on reproduction in F. candida. Wolbachia infection was removed by antibiotic and heat treatment, and quantitative PCR techniques confirmed the success of the treatments. Complete loss of Wolbachia-infection led to the production of normal clutch sizes, but was associated with full egg hatching failure. Our results demonstrate that F. candida is strictly dependent on Wolbachia to produce viable offspring. This is one of the few cases of obligatory Wolbachia infection in arthropods. Our data suggest a unique mechanism underlying Wolbachia-dependence of egg development. One of our more salient results is that hatching success increased in consecutive egg clutches of antibiotic-treated individuals, probably due to restoration of bacterial densities over time. These observations suggest that reproduction in F. candida is a threshold effect requiring a critical Wolbachia density as is hypothesized by the bacterial dosage model. Quantitative PCR analysis showed that heat or antibiotic treated individuals with egg hatching failure had low average bacterial densities, but bacterial densities were not significantly different from those of treated individuals with successfully eclosing eggs. Additional experiments with partially cured F. candida are needed to prove the dosage model. © Springer Science+Business Media B.V. 2008

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