Comparative Analysis of Symbiotic Bacterial Diversity and Sublethal Effects of Nitenpyram Against Two Different Cotton Aphids

Symbiotic bacteria in insects are known to play crucial roles in detoxification metabolism and adaptation to host plant secondary metabolites. In the cotton-growing region of Xinjiang, China, the <i>Ap. gossypii</i> and the <i>Ac. gossypii</i> exhibit significant differences in sensitivity or resistance to pesticides. However, whether their detoxification-related symbiotic bacteria change under insecticide stress remains unclear. This study assessed the toxicity of nitenpyram to both aphid species and the effects of LC₂₀ treatment on their growth, development, and reproduction. Bacterial community dynamics across generations (G0-G2) were analyzed by 16S rRNA gene amplicon sequencing. The LC₂₀ of nitenpyram reduced the longevity and fecundity of the parent generation in both species. In <i>Ap. gossypii</i>, the intrinsic rate of increase (<i>r_m</i>), net reproductive rate (<i>R</i>₀), and finite rate of increase (<i>λ</i>) increased in the G1-G2 generations, whereas these parameters significantly decreased in <i>Ac. gossypii</i>. By the G3 generation, biological parameters in both species showed no significant differences compared to the control. Nitenpyram disrupted the stability of symbiotic bacterial communities in both aphids. In <i>Ac. gossypii</i>, <i>Sphingomonas</i>, a genus with detoxification potential, was consistently suppressed in G1-G2, while the abundance of the primary symbiont <i>Buchnera</i> initially decreased sharply and subsequently recovered. In contrast, the bacterial community in <i>Ap. gossypii</i> remained largely stable. These findings indicate that sublethal concentrations of nitenpyram exert distinct transgenerational effects on the two aphid species and disrupt the stability of their symbiotic bacterial communities.