bacteria are cytoplasmic endosymbionts with a wide range of effects on their hosts and are known to infect two major invertebrate groups, arthropods and nematodes. In arthropods alter host reproduction, causing unidirectional and bidirectional cytoplasmic incompatibility, parthenogenesis, feminization, and embryonic male killing. variation in reproductive effects is indicative of a high degree of evolutionary plasticity. As many as 75% of arthropods may be infected with , which in addition to affecting reproduction, can also directly affect host fitness by either increasing or decreasing survival and fecundity. We review the dynamics of embryonic male-killing, including effects on insect mating behavior, as well as the distribution and implication of infections in filarial nematodes.

Arthropod host– phylogenies are not congruent, which is suggestive of horizontal transmission. The opposite has been shown in nematode- phylogenies, indicative of long-term association and vertical transmission. Multiple levels of parasitism within arthropods may promote horizontal transmission. Bacteriophage WO has recently been identified and is found in all -infected insect hosts so far examined. Extensive horizontal transmission of the phage occurs between different strains within a host as well as between in different hosts. The phage genome may carry genes important in determining both the effect of on arthropod host reproduction and host fitness and fecundity. The extensive horizontal transmission of the phage may explain the plasticity of effect on arthropod hosts.


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  • Article Type: Review Article
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