Central Sericultural Research & Training Institute, Mysore ?570008, Karnataka, India.
A bivoltine silkworm hybrid, KA x NB4D2 was treated with the juvenoid R394 (Ethyl-9 cyclohexyl-3,7-dimethyl-2,4-nonadienoate) at a dose of 0.039 nl/larva at 24, 48, 72 and 96 h of 5th instar for silk yield improvement. Treatment specific significant increase was observed in the cocoon and shell weight with no such marked variation in the shell percentage. Notable changes were also seen in traits such as larval duration, larval weight and silk gland weight in the treated silkworm. Total protein, total carbohydrate and total lipid were analyzed in the posterior silk gland (PSG), haemolymph and fat body of fully grown larvae. The result indicated that the content of these primary metabolites varied significantly in the selected tissues depending on the time of juvenoid application. The highest content of protein in the haemolymph and silk gland was in the larvae treated at 72 h whereas the fat body protein content was lowest in the same group. The total carbohydrate was recorded lowest in the 72 h treated larvae as against the highest in the control both in haemolymph and fat body with no significant change in PSG. The total lipid content did not show any notable variation in the concentration on juvenoid administration except in the silk gland treated up to 72 h which showed a decline. The result indicates that the juvenoid induces tissue specific responses in terms of turnover in primary metabolites.