Extrinsic and intrinsic control of diapause termination in the Colorado potato beetle

K.S. Lefevere

Research output: Thesisinternal PhD, WU

Abstract

The adult <u>Leptinotarsa</u><u>decemlineata</u> enters a winter diapause, which is mainly induced by short photoperiod. The effects of environmental factors (such as temperature, humidity, daylength and food) on the behaviour and the metabolism of some haemolymph components, as for example the juvenile hormone, were analysed in diapausing and post- diapausing females. During diapause three consecutive phases could be distinguished, based on changing response to temperature: 'diapause development' or true diapause, followed by a quiescence which is facultative, and a transient phase of post-diapause development leading to emergence from the soil (or diapause termination). After diapause, high metabolic rates are resumed and postdiapause development culminates in reproduction. The endocrine control of the termination of diapause was investigated by means of hormonal injections. Only the combined injections of 20-hydroxyecdysone and juvenile caused a temporary break of diapause only, lasting as long as the JH titre in haemolymph was high. 20-Hydroxyecdysone (20-HE) injected before JH suppresses the effects of exogenous JH on the endogenous metabolism of JH. It is suggested that 20-HE could be responsible for triggering the programme for diapause termination by the brain. Allatectomy experiments after diapause confirm the role of JH in reproduction and reveal the endocrine control of the Induction of a second diapause. The presented results corroborate the theory that the brain is the primary organ controlling diapause.<p><TT></TT>
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
Supervisors/Advisors
  • Schoonhoven, L.M., Promotor, External person
  • de Kort, C.A.D., Promotor, External person
Award date12 Jan 1988
Place of PublicationS.l.
Publisher
Publication statusPublished - 1988

Keywords

  • Chrysomelidae
  • diapause
  • hibernation
  • aestivation

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