Relationship between juvenile hormone and ecdysteroids in larval-pupal development of Trichoplusia ni (Lepidoptera: Noctuiidae)

R. A. Newitt, B. D. Hammock

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The haemolymph ecdysteroid titre during the late last stadium of the cabbage looper moth, Trichoplusia ni, was monitored in the presence of experimentally altered juvenile hormone levels to test the hypothesis that the appearance of a prepupal burst of juvenile hormone enhances prothoracic gland activity. Two peaks of ecdysteroid activity were detected in the haemolymph of last-stadium larvae (55 ng/ml and 950 ng/ml) with 20-hydroxyecdysone the most prevalent ecdysteroid. Treatment of post-feeding late last-stadium larvae with juvenile hormone I or the juvenoids, methoprene or epofenonane, had no significant effect on the timing or character of pupation. Application of juvenile hormone I to neck-ligated late last-stadium larvae failed to restore peak ecdysteroid levels to those of unligated controls. Application of the anti-juvenile hormone compounds, fluoromevalonolactone or 3,3-dichloro-2-propenyl hexanoate, disrupted metamorphosis causing delays in tanning and the formation of abnormal pupae. Yet, corresponding deviations in the timing or magnitude of ecdysteroid levels or in the conversion of ecdysone to 20-hydroxyecdysone were not observed. When early last-stadium larvae were treated with the juvenile hormone esterase inhibitor, 3-octylthio-1,1,1-trifluoro-2-propanone, shifts in the timing of peak ecdysteroid levels, coincident with delayed pupation, were observed. These results suggest that the prepupal prothoracic glands of T. ni may be considerably less sensitive to changes in the endogenous juvenile hormone titre by the time larvae have begun to wander, even though treatment at this time may still produce toxic effects that influence the success of ecdysis and/or resultant pupal morphology.

Original languageEnglish (US)
Pages (from-to)835-844
Number of pages10
JournalJournal of Insect Physiology
Volume32
Issue number10
DOIs
StatePublished - 1986

Keywords

  • ecdysteroids
  • Insect metamorphosis
  • juvenile hormone

ASJC Scopus subject areas

  • Insect Science
  • Physiology

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