Abstract
Juvenile hormone analogues have been tested as insect growth regulators in silkworm (Bombyx mori), seeking an increment of silk production. These chemical products, when applied in small or moderate rates, promote the extension of the last larval instar. To understand the physiologic consequences on silk production by the silkworm strain C115 x N108, the application of methoprene, a juvenile hormone analogue, was performed to evaluate its effects on larval development and silk production. Methoprene was topically applied 48h after the fourth larval ecdysis, on the dorsal integument of the 2nd thoracic segment of the insects, at seven rates between 0 and 20 ng a.i. Methoprene influenced positively the duration of the fifth instar and the weight gain of the insects. The application of 1ng methoprene resulted in the heaviest silkglands, cocoons, shell cocoons and pupae weights. Comparatively to the control, the increment on silk production (approximately 24%) by the use of 1ng methoprene was more accentuated than the corresponding negative effects on the cocooning rate (approximately 12%).
Highlights
The ecdysis process in insects is regulated by two hormones, one produced by neurosecretory cells in the brain and another by the prothoracic glands
Juvenile hormone analogues have been tested in Bombyx mori as insect growth regulators in order to increase silk production (Akai et al, 1984, 1988; Kajiura et al, 1987; Kajiura & Yamashita, 1989; Chowdhary et al, 1990; Cappellozza et al, 1997)
The first studies with juvenile hormone analogues in B. mori were accomplished through topical applications on the insect (Akai et al, 1971, 1973; Murakoshi et al, 1972)
Summary
The ecdysis process in insects is regulated by two hormones, one produced by neurosecretory cells in the brain (prothoracicotropic hormone) and another by the prothoracic glands (ecdysone). Juvenile hormone analogues have been tested in Bombyx mori as insect growth regulators in order to increase silk production (Akai et al, 1984, 1988; Kajiura et al, 1987; Kajiura & Yamashita, 1989; Chowdhary et al, 1990; Cappellozza et al, 1997). These chemical products, when applied in diminute and appropriate rates, promote the extension of the larval period, when the insect feeds. The present study sought to determine the effects of the topical application of rates of methoprene on the larval development and silk production of C115xN108 silkworm larvae
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