Abstract: The silkworm Bombyx mori is an egg-diapause insect. There are no morphological changes, organ development and tissue differentiation during diapause stage. However, its physiological metabolism is still in progress. In order to further research the diapause mechanism, the change in activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), pyruvate kinase (PK, EC 2.7.1.40), acetylcholine esterase(AchE, EC 3.1.1.7) and lactate dehydrogenase (LDH, EC 1.1.1.28) in the early embryonic stage of diapause eggs, diapause eggs with instant hydrochloric acid (HCl) soaking and non-diapause eggs were detected in this study. The results showed that the activities of SOD, CAT, PK and AChE in the HClsoaked eggs, from 1 d to 7 d, increased from 56 517.00 U/g to 81 986.94 U/g, 14.98 U/g to 106.90 U/g, 25.19 U/g to 181.70 U/g, and 17.88 U/g to 287.86 U/g, respectively, while that of LDH decreased from 169.96 U/g to 122.82 U/g. In the non-diapause eggs during the same period, the activities of SOD and LDH decreased from 86 417.99 U/g to 66 024.19 U/g and 169.07 U/g to 135.02 U/g, respectively; the activities of CAT, PK and AchE, however, increased from 1.47 U/g to 44.37 U/g, 20.56 U/g to 92.09 U/g, and 21.40 U/g to 99.17 U/g, respectively. In the diapause eggs, the activities of SOD and AChE were stable; the CAT activity was raised but LDH activity was decreased with the embryonic development; and the PK activity was raised in the first four days of the embryonic development and remained stable afterwards. Understanding the change of related enzyme activities among diapause, non-diapause and HCl-soaked silkworm eggs in the embryonic development will help to reveal the diapause mechanism.

Key words: Bombyx mori, diapause, diapause eggs, non-diapause eggs, instant hydrochloric acid soaking, enzyme activity