Removing symbioticWolbachiabacteria specifically inhibits oogenesis in a parasitic wasp

Abstract

Wolbachia are bacteria that live in the cells of various invertebrate species to which they cause a wide range of effects on physiology and reproduction. We investigated the effect of Wolbachia infection in the parasitic wasp, Asobara tabida Nees (Hymenoptera, Braconidae). In the 13 populations tested, all individuals proved to be infected by Wolbachia. The removal of Wolbachia by antibiotic treatment had a totally unexpected effect-aposymbiotic female wasps were completely incapable of producing mature oocytes and therefore could not reproduce. In contrast, oogenesis was not affected in treated Asobara citri, a closely related species that does not harbor Wolbachia. No difference between natural symbiotic and cured individuals was found for other adult traits including male fertility, locomotor activity, and size, indicating that the effect on oogenesis is highly specific. We argue that indirect effects of the treatments used in our study (antibiotic toxicity or production of toxic agents) are very unlikely to explain the sterility of females, and we present results showing a direct relationship between oocyte production and Wolbachia density in females. We conclude that Wolbachia is necessary for oogenesis in these A. tabida strains, and this association would seem to be the first example of a transition from facultative to obligatory symbiosis in arthropod-Wolbachia associations.

Cloning and sequencing of wsp encoding gene fragments reveals a diversity of co-infecting Wolbachia strains in Acromyrmex leafcutter ants

“…This observation has been taken as indirect support for an effect on the hostÕs sex ratio via partial male killing . The A strain infection of A. insinuator (the InsA strain identified here), on the other hand, has been found to be equally common in males and gynes , which precludes any effects on the hostÕs sex ratio, and suggests that it may have other effects, such as cytoplasmic incompatibility or enhanced fecundity (Dedeine et al, 2001). A hypothetical prediction about the phenotypes associated with the B strains is more difficult, because multiple B strains occur in each host, and no information exists on the prevalence of each of the strains.…”

“…It is known to selfishly enhance its matrilineal transmission through various alterations of host reproduction, including feminisation (reviewed by Rigaud, 1997), thelytokous parthenogenesis (reviewed by Stouthamer, 1997), male-killing (MK, reviewed by Stevens et al, 2001) and cytoplasmic incompatibility (CI, reviewed in Hoffmann and Turelli, 1997). Recently, fecundity enhancing effects have also been reported (Dedeine et al, 2001). Wolbachia therefore covers the entire range of endosymbiotic interactions, from parasitism to mutualism.…”

Intra-Individual Coexistence of a Wolbachia Strain Required for Host Oogenesis With Two Strains Inducing Cytoplasmic Incompatibility in the Wasp Asobara Tabida

“…Different hypotheses have already been suggested on this issue (Charlat and Merçot 2001;Dedeine et al 2001Dedeine et al , 2003. One hypothesis is that the strain wAtab3 produces a toxic molecule in host females that is transmitted to all offspring via the egg cytoplasm, which can only be rescued by female offspring inheriting wAtab3.…”

“…Surprisingly, the dependence of A. tabida on Wolbachia seems to be specific for oogenesis. Aposymbiotic males are fertile and, except for their inability to produce eggs, aposymbiotic females appear to have a normal overall physiological state (normal size, weight, locomotor activity and behavior; Dedeine et al 2001). Exactly how the dependence of A. tabida on Wolbachia infection has evolved remains an open question.…”

Variable male potential rate of reproduction: high male mating capacity as an adaptation to parasite–induced excess of females?

“…Wolbachia are intracytoplasmic inherited bacteria which infect a large number of arthropod and nematode species (Rousset et al 1992;Werren et al 1995;Bandi et al 1998). These bacteria are able to alter the reproductive biology of their hosts in many ways, all increasing their spread within host populations (Werren & O'Neill 1997;Stouthamer et al 1999;Dedeine et al 2001). The impact of such 'reproductive parasites' on host reproductive effort or strategy has been investigated rarely (e.g.…”