Bacterial endosymbionts play important roles in ecological traits of aphids. In
this study, we characterize the bacterial endosymbionts of A. gossypii collected in Karaj,
Iran and their role in the performance of the aphid. Our results indicated that beside Buchnera
aphidicola, A. gossypii, also harbors both Hamiltonella defensa and Arsenophonus
sp. Quantitative PCR (qPCR) results revealed that the populations of the endosymbionts
increased throughout nymphal development up to adult emergence; thereafter, populations
of Buchnera and Arsenophonus were diminished while the density of H. defensa constantly
increased. Buchnera reduction caused prolonged development and no progeny production.
Furthermore, secondary symbiont reduction led to reduction of the total life span and
intrinsic rate of natural increase as well as appearance of the deformed dead offspring in
comparison with the control insects. Reduction of the secondary symbionts did not affect
parasitism rate of the aphid by the parasitic wasp Aphidius matricariae. Together these
findings showed that H. defensa and Arsenophonus contributed to the fitness of A. gossypii
by enhancing its performance, but not through parasitoid resistance.
