Growth parameters associated with endocrine events in larval Trichoplusia ni (Hübner) and timing of these events with developmental markers

D. Jones, G. Jones, B. D. Hammock

Research output: Contribution to journalArticle

100 Scopus citations

Abstract

Numerous behavioural and morphological markers were found during the last instar of Trichoplusia ni which permit selection of highly synchronous groups of larvae for physiological or biochemical experiments. Growth parameters were also examined and it was found that the occurrence of a 6th instar was associated with a head-capsule width below the critical threshold of 1.66 mm. Starvation experiments indicated that the critical body weight triggering the first release of prothoracicotropic hormone (PTTH) was not the same for all larvae and was associated closely with a critical ratio of body size: head-capsule size and/or body size: initial body size at the beginning of the instar. The time of prothoracicotropic hormone-ecdysone release in preultimate instars was also associated with a similarly calculated ratio. The ratio was very similar from instar to instar. Neck or thoracic-abdominal ligation of larvae attaining various markers provided indications of times of release of critical amounts of prothoracicotropic hormone, ecdysone and juvenile hormone. The time of peak juvenile-hormone-esterase (JHE) activity in the haemolymph during the prepupal stage was determined with these markers.

Original languageEnglish (US)
Pages (from-to)779-788
Number of pages10
JournalJournal of Insect Physiology
Volume27
Issue number11
DOIs
StatePublished - 1981

Keywords

  • ecdysone
  • growth parameters
  • JH esterase
  • juvenile hormone
  • physiological markers
  • PTTH
  • supernumerary moults
  • Trichoplusia ni

ASJC Scopus subject areas

  • Insect Science
  • Physiology

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