Growth parameters associated with endocrine events in larval Trichoplusia ni (Hübner) and timing of these events with developmental markers
1981; Elsevier BV; Volume: 27; Issue: 11 Linguagem: Inglês
10.1016/0022-1910(81)90068-8
ISSN1879-1611
AutoresDonald R. Jones, Gareth Jones, Bruce D. Hammock,
Tópico(s)Plant and animal studies
ResumoNumerous 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.
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