A Possible Novel Strategy for Reproductive Manipulation by an Endosymbiont

Abstract

Reproductive manipulation is commonly seen in insects infected by maternally inherited endosymbionts. These endosymbionts have adopted several strategies to manipulate their hosts in order to guarantee their transmission into the next host generation. Cytoplasmic incompatibility (CI) is the most common method of manipulation and occurs when an infected male mates with an uninfected female. Such matings result in embryonic mortality of offspring, which is observed as a decrease in the hatch rate of eggs, and provides infected females in a population a reproductive advantage over uninfected females. Another form of manipulation is the selective killing of the male offspring of infected females. This type of manipulation, referred to as male killing, occurs in several strains of the bacterial endosymbiont Spiroplasma, which infects several Drosophila species. However, not all Spiroplasma that infect Drosophila cause male death, but other forms of manipulation have not yet been examined. Here, we determined whether the non-male killing Spiroplasma strain Hyd 1(native to Drosophila hydei) induces CI in D. melanogaster. We ran several crosses of D. melanogaster infected with Spiroplasma strain Hyd1, and found no evidence of CI since hatch rates did not differ from control crosses. Instead, we observed a significant decrease in egg production by females from crosses in which only the male was infected in comparison to the other crosses. Although this strain of Spiroplasma does not exhibit the conventional manipulation strategy of CI, these results could indicate an alternative strategy for achieving the goal of increasing the endosymbiont?s frequency in a host population by decreasing the fecundity of uninfected female hosts.