Sexual Sabotage by the Bacterial Parasite Wolbachia

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Reproductive Manipulations on Parasitoids

Transmitted through the reproductive systems of insects, crustaceans, mites and nematode worms, the Wolbachia is endocellular bacteria whose interactions between the host and itself are far from mutualistic (Hurst & Randerson 2002:44). The bacteria are unable to be transmitted through sperm so they invade the cytoplasm of eggs in female hosts to be capable of increasing their numbers. The Wolbachia have a variety of reproductive manipulations that enable successful transmission such as feminization, male killing, parthenogenesis and also cytoplasmic incompatibility. Owing to these extreme host manipulations the Wolbachia are possibly initiating reproductive isolation in host invertebrates and massively distorting sex ratios for their own advantage (Hurst & Randerson 2002:44; Werren 1997: 1).

Reproductive Manipulations of Host

Wolbachia are able to manipulate the reproduction mechanisms of its hosts by provoking male killing, feminization, parthenogenesis and also cytoplasmic incompatibility (Hurst & Randerson 2002:44). As mentioned earlier Wolbachia are unable to be transmitted via sperm and as a result female hosts are of crucial importance to the parasite.

Male Killing: In some groups of African Butterfly Acraea encedon, the widespread pill bug Armidillidium vulgare and the common two-spot ladybug Adilia bipunctata the Wolbachia eradicate unhatched male hosts in a population, known as male killing as they have no chance of being transmitted through sperm. This benefits the survival of sibling female hosts as they are no longer in competition with brothers for food and sibling cannibalism and reduces the incidence mutations from inbreeding. By killing males hosts the Wolbachia are able to increase female numbers in a population, thus improving their chances of being transmitted (Hurst & Randerson 2002:44; Schulenburg et al. 2002:1).

Feminisation: Another reproductive method the Wolbachia bacteria employ is that they are able to convert genetic males of a population such as pill bugs and the...