Role of haemolymph biochemical constituents and brain proteins in maintenance of pupal diapause in Daba bivoltine ecorace of tropical tasar silkworm Antheraea mylitta Drury

Mishra, P. K.; Kumar, Dinesh; Jaiswal, Lily; Kumar, Ashutosh; Singh, B. M. K.; Sharan, S. K.; Pandey, Jay Prakash; Prasad, B. C.
December 2009
Journal of Ecophysiology & Occupational Health;Dec2009, Vol. 9 Issue 3/4, p243
Tropical tasar silkworm Antheraea mylitta Drury (Lepidoptera: Saturniidae) is one of the commercially exploited non-mulberry silkworm in tropical India. Since time immemorial the aboriginals of India use to rear the silkworms in their natural abode besides collecting bulk of cocoons from the forest area. The diapausing Daba bivoltine pupae remain in facultative pupal diapause state for 7 to 8 months (Nov.-June). During diapause period erratic emergence of moths takes place besides pupal mortality, unsynchronised emergence of male and female moths. It is estimated that tropical tasar silkworm industry is faced with the problem of loss of seed material due to pupal mortality (10-20 %) erratic (10-15 %), un-seasonal (10-20 %) and unsynchronised (10-20 %) emergence. This leads to the losses during seed production and overall production/ productivity. To understand the root cause of these the physiology of diapause needs to be studied at biochemical and molecular level in relation with environmental and nutritional factors responsible for induction and maintenance of diapause among population. Haemolymph is the only medium which caters to the energy reserves for any physiological mechanism in an insect. To explore the physiology of diapause to work out a temperature sensitive diapause termination state, the haemolymph biochemical parameters like glycerol, trehalose, glycogen, quantitative total proteins and free amino acids were estimated through out the pupal diapause period of Daba bivoltine ecorace. It was observed that the level of protein was high through out the diapause period. At the fag end of diapause at 190 to 200 days age of pupae, depletion in the level of protein was observed. The amino acids levels showed a fluctuating trend through out diapause development. Accumulation of glycogen was observed through out diapause period and it went down once pupae attained the age of 190 to 200 days. Resumption in the level of glycogen was observed once adult emergence was nearing by 215 to 220 days. Similarly, through out diapause period the accumulation of Glycerol in the haemolymph was observed which went down when pupae attained the age of 190 to 200 days. Contrary to this, the level of trehalose remained at low through diapause period and went up at 190 to 200 days of age of pupae. These findings indicate that when diapausing pupae of Daba bivoltine pupae attain the age of 195 to 200 days a shift is observed from deeper diapause state to diapause termination. This stage can be exploited for low temperature treatment to regulate the emergence of moths in grainages in order to have more couplings and enhanced egg production. Studies in this direction are under progress. Pupal diapause is mediated by the brain prothracicotropic complex and non-receipt of brain signals in the form PTTH leads to pupal diapause in adverse seasons in insects. Hence through SDS PAGE presence of brain proteins were also studied. It was found that in diapausing generation, in early diapause period (Day 0 to day 15) and mid diapause period (Day 30 to Day 150) and late diapause period (Day 150 to 165) and during termination period of diapause development period (day 180 to day 210) accumulation of four diapause specific proteins having molecular weight range of 80, 46, 38 (female specific), 31 and 18kDa was observed. These proteins were not present in non-diapausing generation. At the fag end of diapause period (after day 195 and at Day 210), the brain proteins profile was alike in both non-diapause and diapause destined generations.


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