Applications of tyroxine and juvenile hormone analog (methoprene) to Bombyx mori larvae have been reported as one of the means to increase the silk production. It is thought that the utilization of these hormones either in combination or single would change the normal pattern of haemolymph ecdysteroid titer. This research has been conducted to evaluate the effect of tyroxine and methoprene hormones to haemolymph ecdysteroid titer pattern during fifth instar of Bombyx mori. Second instar larvae were fed with mulberry leaves that had been treated with 1500 ppm of tyroxine. The larvae were then allowed to molt into third and fourth instars without treatment. Seventy-two hours after molting to fifth instar, larvae were injected by 10 µl of methoprene, with concentration of 15 or 25 ppm. Titer of ecdysteroid was detected by HPLC. The result showed that an alteration of ecdysteroid titer pattern occurred on larvae which had been treated by tyroxine or tyroxine-methoprene combination, when compared to the control group. Ecdysteroid titer was detected 2 days earlier and the titer was higher on larvae treated by tyroxine when compared to the control group. It appears that combination of tyroxine and methoprene treatment suppresses ecdysteroid titer. It was suggested by the fact that the titer of ecdysteroid decreased significantly soon after methoprene injection, and before reaching the maximum peak of the titer.
Species 1: Lepidoptera Bombycidae Bombyx mori (silkworm)
Keywords: methoprene, silk
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