Abstract: 【Aim】 This study aims to investigate the defensive responses in the Chinese tussah moth, Antheraea pernyi induced by different exogenous microbes so as to obtain measures for the disease control and breeding of the moth. 【Methods】 Gram-positive bacteria Bacillus thuringeinsis (Bt) and gram-negative bacteria Escherichia coli (Ec) were selected as the exogenous microorganisms. The concentration of the bacterial solution was adjusted to 10⁶-10⁸ cfu/mL. A. pernyi pupae were induced by inactivated bacteriafor 24, 48, 72 and 96 h, and the physiological indices including hemolymph protein content and the PO activity, CAT activity, antibacterial activity and lysozyme activity in hemolymph were analyzed. 【Results】 Ec and Bt induced prominent changes in several physiological indices of A. pernyi pupae. But the patterns of physiological indices induced by the two bacteria were distinctly different. Haemolymph protein content in A. pernyi pupae increased at 72 h after induction by high concentrations of Ec, while it increased at 24, 48 and 96 h after induction by Bt at various concentrations. The activities of immune defense key enzymes including PO and CAT changed remarkably. The PO activities increased first and then decreased, while the CAT activities showed an increase-decrease-increase tendency after induction by Ec. The PO activities showed an increase-decrease-increase fluctuating pattern, while the CAT activities had no obvious alteration after induction by Bt. Antibacterial activity assay showed that Ec and Bt induced a significant increase in antibacterial activity and lysozyme activity in crude extracts of pupae. But the peak time of antibacterial activity and lysozyme activity was distinctly different. 【Conclusion】 The research results indicated that different treatments of Ec and Bt can induce distinct defense responses in A. pernyi pupae, and the variation patterns of physiological indices are related to different kinds of microorganisms and treatment time and concentration. It is speculated that gram positive bacteria and gram negative bacteria have different induced defense mechanisms. We propose that the several physiological indices can be used as markers for immune defense response to exogenous microbes in A. pernyi.

Key words: Antheraea pernyi, Escherichia coli; Bacillus thuringiensis, immunity, enzyme activity