Abstract: 【Aim】 Understanding the response patterns of insects after immunity induction is a basis to reveal the mechanisms of adaptive immune response, immune trade-offs and immune priming. The study aims to clarify the dynamic changes of the immune response in Octodonta nipae (Maulik) adults induced by bacteria and the response differences between males and females. 【Methods】 The cell-wall extract lipopolysaccharide (LPS) of gram negative bacteria was injected into the body cavity of O. nipae adults to induce their immune response. The activities of phenoloxidase (PO) and antimicrobial peptide (AMPs), which play an important role in insect innate immunity, were assayed at different time post induction. 【Results】 The PO activity and the antibacterial activity of AMPs in O. nipae  adults were significantly induced by 2.5 mg/mL×138 nL LPS in a certain time period, and the response models were different between females and males. The PO activities in LPS-induced female (4-10 h post induction) and male adults (0.1-10 h post induction), as well as the antibacterial activity of AMPs in LPS-induced female (12-48 h post induction) and male adults (4-48 h post induction), were significant higher than those of the blank control, respectively. LPS induced a faster increase of PO activity than of AMPs activity, but the increase of AMPs activity lasted for a longer time. Before immune induction, the PO activity and the antibacterial activity of AMPs in female adults were significant higher than those in male adults; and after immune induction the PO activity and the antibacterial activity of AMPs in female adults also had a higher top level. 【Conclusion】 The results suggest that LPS can induce a dynamic immune response in O. nipae adults, which is different between males and females. Our findings provide a foundation for further studies on adaptive immune response of O. nipae in the new invading environment and to develop an effective strategy to control O. nipae.

Key words: Octodonta nipae, immune induction, lipopolysaccharide, antimicrobial peptide, phenoloxidase activity, antibacterial activity, gender difference