Applying fenoxycarb at the penultimate instar triggers an additional ecdysteroid surge and induces perfect extra larval molting in the silkworm

General and Comparative Endocrinology
Manabu Kamimura, Makoto Kiuchi

Abstract

When the juvenile hormone analog fenoxycarb was topically applied to the silkworm Bombyx mori at the beginning of the 3rd or 4th (penultimate) instar, an extra larval molt was induced. The 5th instar period was shortened to about 5 days and the extra 6th instar ranged from 8 to more than 20 days, depending on the dose applied. Starvation before fenoxycarb treatment strongly enhanced the incidence of extra molting up to 100%. When 1 ng was applied in the 4th instar after a 2-day starvation, most larvae underwent an extra molt, metamorphosed to pupae, then to fertile adults. Combining starvation and fenoxycarb application thus induces a perfect extra molt efficiently. In perfect extra molting larvae, profiles of total ecdysteroid titer during the 4th and 5th instars were similar to that during the 4th instar in the control, and the ecdysteroid profile during the extra 6th instar was similar to that during the control 5th (last) instar. At ecdysteroid peaks, 20-hydroxyecdysone (20E) and ecdysone (E), generally regarded as the active molting hormone and its precursor, had similar titers in the 6th instar, whereas E was much less than 20E in the 4th and 5th instars in the extra molting larvae. E was also abundant only in the last la...Continue Reading

References

Jul 2, 2003·Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology·Michiyoshi TakahashiManabu Kamimura
Sep 12, 2012·Journal of Insect Science·Takaaki DaimonToru Shimada
Nov 8, 2005·Journal of Insect Physiology·Yuichi NakaharaManabu Kamimura
Apr 25, 2015·Journal of Insect Physiology·Mari H OgiharaHiroshi Kataoka
Dec 19, 2002·Archives of Insect Biochemistry and Physiology·Makoto KiuchiManabu Kamimura

Citations

Mar 1, 1985·Annals of Internal Medicine·J H Oppenheimer
Aug 1, 1987·Endocrine Reviews·J H OppenheimerH C Freake
Jan 24, 1998·Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology·S SatakeAkira Mizoguchi
Jun 14, 2000·General and Comparative Endocrinology·M MasumuraAkira Mizoguchi
Jun 22, 2000·Archives of Insect Biochemistry and Physiology·S SatakeAkira Mizoguchi

Related Concepts

Fertility
Molting
Bombyx
Larva
Drug Interactions
Pupa
Ecdysone
Gene Expression Regulation, Developmental
Fenoxycarb
Ecdysteroids

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