A comprehensive study of the changes in ecdysteroid levels during the feeding phase of fifth instar larvae of the silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Abstract

Abstract. The present study describes changes in haemolymph ecdysteroid levels during the feeding phase of fifth instar larvae of Bombyx mori. A small and sharp peak in ecdysteroid level was recorded on day 4 when larvae had already reached the critical weight (2.76 ± 0.11 g) for metamorphosis. Food deprivation of larvae from day 4 resulted in an increase in the ecdysteroid level. Injection of insulin in both 1 day (before reaching critical weight) and 4 day (after reaching critical weight) old fed larvae resulted in an increase in the ecdysteroid level. However, when deprived of food only the haemolymph ecdysteroid levels of 4 day old larvae respond to an injection of insulin. The hormone level was also increased by treating 1day old larvae with a juvenile hormone analogue, but again, like insulin, only the fed larvae were affected by this treatment. Neck-and thorax-ligated 4 day old larvae had decreased ecdysteroid levels compared to both fed and food deprived larvae. However, a significant increase in ecdysteroid level was recorded in both neck-and thorax-ligated larvae injected with insulin. The injection of 20-hydroxyecdysone into 4 day old larvae resulted in an increase in the level of this substance in the haemolymph of fed and food deprived larvae, but the level was significantly higher in neck-and thoraxligated la rvae. The data, thus, indicates that ecdysteroid levels vary both in relation to the critical weight of the larvae and its nutritional status, and insulin might also play an important role in regulating the level of ecdysteroid.

Larvicidal efficacy of Adiantobischrysene from Adiantum latifolium against Oryctes rhinoceros through disrupting metamorphosis and impeding microbial mediated digestion

“…The growth and development of an insect is under the control of various intrinsic and extrinsic factors such as hormones and nutrition . Ecdysone and its active metabolite 20E, collectively known as ecdysteroids, are essential for controlling development, for example moulting, metamorphosis and diapause .…”

“…The growth and development of an insect is under the control of various intrinsic and extrinsic factors such as hormones and nutrition. 10 Ecdysone and its active metabolite 20E, collectively known as ecdysteroids, are essential for controlling development, for example moulting, metamorphosis and diapause. 37 Surpassing a critical weight results in the initiation of an endocrine cascade for wileyonlinelibrary.com/journal/ps metamorphosis, as originally described for the tobacco hornworm, Manduca sexta.…”

“…The growth and development of insects are under the control of various intrinsic and extrinsic factors such as hormones and nutrition . In many insect species, the availability of food during larval development is critical for metamorphosis .…”

“…The growth and development of insects are under the control of various intrinsic and extrinsic factors such as hormones and nutrition. 10 In many insect species, the availability of food during larval development is critical for metamorphosis. 11 Third-instar larvae of O. rhinoceros may undergo precocious metamorphosis on prolonged starvation provided they have reached a critical weight of 12.17 g for pupation and fail to pupate if the reduction in body weight is found to be beyond a critical level.…”

Azadirachtin induced apoptosis in the prothoracic gland in Bombyx mori and a pronounced Ca2+ release effect in Sf9 cells

“…Azadirachtin is considered to be the most important active principle present in neem 17 . Fifth-instar larvae are committed to ecdysone release 18 , after which period the prothoracic gland may release ecdysone even in the absence of the brain complex 19 . The effect of azadirachtin on the development and cocooning of silkworms was examined on fifth instar larvae of silkworms, and the results showed that azadirachtin could significantly inhibit cocooning behavior and development of silkworms.…”