Control of moulting and metamorphosis in the tobacco hornworm, Manduca sexta (L.): cessation of juvenile hormone secretion as a trigger for pupation.
نویسندگان
چکیده
During the final larval instar of the tobacco hornworm the presence of juvenile hormone (JH) inhibits the secretion of the brain's prothoracicotropic hormone (PTTH). The corpora allata cease to secrete JH when the larvae attain a weight of approximately 5 g. The JH is cleared from the haemolymph in about 24 h. This process in itself renders the brain competent to release PTTH. The actual release of PTTH occurs at the very first photoperiodic gate after the JH has disappeared from the haemolymph. A functional failure of this normal mechanism is apparently responsible for the developmental standstill of Lepidoptera which diapause as mature larvae.
منابع مشابه
Physiology of insect rhythms. 3. The temporal organization of the endocrine events underlying pupation of the tobacco hornworm.
The moulting process of insects is governed by the interaction of three hormones: prothoracicotropic hormone (PTTH), juvenile hormone, and ecdysone (see Doane, 1973; Wyatt, 1972; Wigglesworth, 1971 for recent reviews). To initiate the moult the brain releases PTTH which causes the secretion of ecdysone from the prothoracic glands. Ecdysone in turn triggers the detachment of the epidermis from t...
متن کاملControl of moulting and metamorphosis in the tobacco hornworm, Manduca sexta (L.): growth of the last-instar larva and the decision to pupate.
The dynamics of growth and the timing of release of the brain's prothoracicotropic hormone (PTTH) in final instar larvae of Manduca sexta are consistent with the following hypothesis. When a 5th-stage larva reaches a critical weight of about 5 g an unidentified process is initiated which requires 24 h to be completed. At the completion of this process the brain is rendered competent to release ...
متن کاملThe role of low levels of juvenile hormone esterase in the metamorphosis of Manduca sexta
The activity of juvenile hormone esterase (JHE) in feeding fifth instar larvae of Manduca sexta increases gradually with larval weight and rises to a peak after larvae pass the critical weight when juvenile hormone secretion ceases. Starvation of larvae of Manduca sexta (L.) that had exceeded the critical weight inhibited peak levels of JHE, but did not delay entry into the wandering stage when...
متن کاملThe release of the prothoracicotropic hormone in the tobacco hornworm, Manduca sexta, is controlled intrinsically by juvenile hormone.
Pupal development is elicited early in the last larval instar of the tobacco hornworm, Manduca sexta (Johannson), by a precise temporal and quantitative increase in the haemolymph titre of 20-hydroxyecdysone. This increase in the titre is referred to as the pupal commitment peak, and it occurs once the titre of juvenile hormone (JH) has dropped. If the haemolymph titre of JH remains elevated at...
متن کاملDevelopmental endocrinology of larval moulting in the tobacco hornworm, Manduca sexta.
A larval moult in the tobacco hornworm, Manduca sexta, involves an endocrine cascade that begins with the release of a cerebral peptide hormone, the prothoracicotropic hormone (PTTH). The release of PTTH is gated, occurs during the scotophase and appears to be developmentally cued. In fourth instar Manduca larvae, PTTH release into the haemolymph occurs as a single burst over a few hours during...
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ورودعنوان ژورنال:
- The Journal of experimental biology
دوره 61 2 شماره
صفحات -
تاریخ انتشار 1974