Effects of gut symbiotic bacteria, Caballeronia insecticola, on reproductive capacity and mating behaviors of insect host, Riptortus pedestris (Hemiptera: Alydidae)

Abstract This study addresses how gut symbiont, Caballeronia insecticola, could change reproductive capacity, mating behaviors, and copulation success of host insect, Riptortus pedestris (Fabricius) (Hemiptera: Alydidae). First, we evaluated symbiotic effects on the female reproductive capacity with varying numbers of males available to a female. Overall, symbiotic females displayed on average a 1.8-fold increase in egg production compared to aposymbiotic individuals. However, eggs from symbiotic females were on average 42% less viable, compared to those from the aposymbiotic, when paired with single male. The decrease in the hatchability was alleviated to 12% when paired with 3 males. Consequently, this yielded significant increase in the number of viable offspring by symbiotic females when multiple males were available. Second, we evaluated symbiotic effects on male morphometric characteristics including hind legs used as weapon, and found significant increases in hind leg sizes associated with symbiosis. Finally, we investigated mating behaviors between a female and 2 males of different symbiotic status. Symbiotic females displayed on average a 1.4-fold increase in the number of copulations compared to the aposymbiotic. From both female types, however, no significant difference was observed in their mate choice and copulation success rate between aposymbiotic and symbiotic males. However, symbiotic females exhibited on average 17% reduction in copulation duration compared to the aposymbiotic. Copulation failure was caused more frequently by female’s rejection than by intruder male’s disruption for both female types. Our study demonstrates that symbiotic females benefit from the symbiosis increasing their reproductive capacity and copulation frequency.