Assessment of Survival and Body Size Variation of Culicoides imicola (Diptera: Ceratopogonidae) as Functions of “Candidatus Cardinium” (Bacteroidetes) Infection Status

Abstract

b "Candidatus Cardinium hertigii" (Bacteroidetes) is a maternally inherited endosymbiont known from several arthropods. Its mechanisms for persistence in host populations are mostly reproductive manipulation, though it has been occasionally reported to improve fitness parameters in several hosts. In Culicoides (Diptera: Ceratopogonidae) biting midges, the prevalence of "Candidatus Cardinium" infection was documented as moderate, with no detectable sex bias. We therefore investigated whether "Candidatus Cardinium" affects important fitness parameters, such as survival and body size, in Culicoides imicola, a dominant vector species. Field-collected midges were trapped and analyzed for survival under different environmental conditions and antibiotic treatment, taking into account "Candidatus Cardinium" infection status and parity status (i.e., parous or nulliparous). Additionally, wing lengths were measured as a proxy parameter for body size and analyzed together with "Candidatus Cardinium" infection data. The findings revealed no difference in survival of Culicoides infected with "Candidatus Cardinium" and that of uninfected midges in both parity states and under all tested conditions: optimal, starvation, heat, and antibiotic treatment. Beyond survival, no wing length difference was found for "Candidatus Cardinium"-infected versus uninfected midges. In aggregate, these findings support our conclusion that "Candidatus Cardinium" does not have an overt effect on the survival and size of adult C. imicola midges. "Candidatus Cardinium" may affect immature stages or may alter adult reproductive performance.

High Ozone (O3) Affects the Fitness Associated with the Microbial Composition and Abundance of Q Biotype Bemisia tabaci

“…A regression equation showed positive correlations between the female ratio and the number of eggs produced by a female and the abundance of Candidatus_Cardinium , which suggests that this symbiont contributes to the regulation of whitefly reproduction by parthenogenesis and feminization. Furthermore, these results are consistent with the fact that Candidatus_Cardinium affects host reproductive fitness but does not have an overt effect on the survival (immunity) and size (growth) of adult Encarsia ( Morag et al, 2013 ). The existence of a strong correlation between the effect of hO 3 on fitness and the abundance of bacteria favors a working hypothesis that the changes in the microbial environments inside of the body and on the surface of the whitefly could be a crucial factor underlying changes in fitness under hO 3 .…”

First detection of Wolbachia-infected Culicoides (Diptera: Ceratopogonidae) in Europe: Wolbachia and Cardinium infection across Culicoides communities revealed in Spain

“…The role for Cardinium infection in arthropod’s fitness remains uncertain to date. In Culicoides , no difference in survival rate was attributed to Cardinium infection for C. imicola in laboratory conditions [ 33 ] . However, the present study widens the known Cardinium infection host range within the genus Culicoides .…”

Detection of Low-Level Cardinium and Wolbachia Infections in Culicoides

“…Although these infections occur at a low level, they may still have a significant impact on their host insect, as has been shown for Wolbachia in Drosophila paulistorum semispecies, which can influence fecundity, sex ratio, and mate discrimination (23). Studies on the effect of Cardinium in C. imicola have found no infection impact on Culicoides survival under optimal, starvation, heat, and antibiotic treatments and no effect on wing size (55). However, detection in that study involved conventional PCR screening, and perhaps an effect on Cardinium was overlooked because low-level endosymbiont infections were not identified or other effects of Cardinium were not characterized.…”