The facultative intracellular symbiont Lariskella is neutral for lifetime fitness and spreads through cytoplasmic incompatibility in the leaf-footed bug, Leptoglossus zonatus (Hemiptera:Coreidae)

Maternally inherited microbial symbionts play important roles in the ecology and reproduction of terrestrial arthropods. We examined the role of the maternally-inherited intracellular symbiont, Lariskella (Rickettsiales: Midichloriaceae), in the leaf-footed bug, Leptoglossus zonatus (Hempitera:Coreidae). Leptoglossus zonatus also harbors an obligate nutritional symbiont, Caballeronia, which is acquired from the environment early in development. To examine the role of Lariskella on bug performance and reproduction as well as possible Lariskella - Caballeronia interactions, we reared bugs in a factorial experiment with both Lariskella and Caballeronia positive and negative treatments. Only Caballeronia negative bugs showed significant developmental delays. Lifetime survival analysis (～120 days) also showed a significant decrease in survival for bugs that lacked Caballeronia, but there were no significant differences between treatments with and without Lariskella. Additional crossing experiments were performed in all possible combinations with and without Lariskella, and showed that Lariskella-negative females produced significantly fewer surviving eggs when mated with Lariskella positive males, consistent with a cytoplasmic incompatibility (CI) phenotype. Finally, comparative genome analysis of Lariskella will determine whether Lariskella manipulates host reproduction with genes homologous to the CI bacterium Wolbachia, the only CI bacterium in which the causal genes are known. These analyses help shed light on the cryptic role of Lariskella in L. zonatus and provide hypotheses to further explain high infection frequencies observed in some other Lariskella-carrying arthropod hosts.