Low H 2 O 2 and enhanced oxidative resistance in the diapause-destined pupa of silkworm, Antheraea mylitta (Lepidoptera:Saturniidae) suggest their possible involvement in dormancy and lifespan extension

Insect diapause is associated with physiological dormancy, extension of life span and an altered developmental programme. Reactive oxygen species, oxidative damaged products and antioxidants are being increasingly linked to such processes in insects. Tropical tasar silkworm, Antheraea mylitta Drury (Lepidoptera:Saturniidae), has an impressive pupal diapause and exhibits a distinct pattern of development in nondiapausing (NDP) pupa compared to that of diapausing (DP) pupa. In this study, we have analysed the amount of hydrogen peroxide (H2O2) and oxidative damaged products along with the levels of antioxidant protection in the hemolymph (HL) and fat body (FB) tissues of developing pupa of A. mylitta from DP and NDP generations having identical chronological age but distinct physiological status. Signature of oxidative predominance was clearly marked in the tissues of diapause-destined pupa as evident from a higher level of lipid peroxidation and protein carbonyl content, despite a lower level of H2O2 in the said group. Specific activity of catalase, exclusively observed in the FB was significantly higher in diapause-destined pupae. Total superoxide dismutase activity was found to be higher in both tissue types of diapause-destined pupae compared to their NDP counterpart. In contrast, pupae committed for diapause displayed less activity for glutathione S-transferase than the NDP group. Reduced glutathione exhibited tissue specificity being higher in the FB of NDP pupae. Findings of this study suggest that low H2O2 pool with a strategic antioxidant protection is associated with induction of dormancy and enhanced oxidative resistance during an extended lifespan.