| | 1 | Author
| Jean-Paul Delbecque, Karel Sláma | Requires cookie* | | | Title
| Ecdysteroid Titres during Autonomous Metamorphosis in a Dermestid Beetle  | | | | Abstract
| The larvae of Dermestes maculatus are able to undergo several moults in complete absence o f the cephalic and prothoracic neuroendocrine system, showing thus spontaneous metamorphosis. Measurements of ecdysteroid contents by radioimmunoassay methods have revealed distinctive larval, prepupal and pupal ecdysteroid peaks, as found in other species where development requires frequent stimulation by the centrally produced hormones. Mass fragmentographic analysis has indicated that more than 80% of the ecdysteroids detected by the radioimmunoassay during the peaks consists of ecdysterone. The prothoracic glands (PG) o f D. maculatus larvae are located in the head capsule and in the cervical region. They can be separated from the body by neck-ligation. Only the larval peak o f ecdysterone can be correlated with PG function. The prepupal and pupal peaks o f ecdysterone are not produced by the central neuroendocrine system. The isolated abdominal fragments o f larvae and pupae positively produce ecdysteroids in the course of their independent development, but this synthesis has been subnormal and occasionally delayed in time. In contrast, the isolated thoracic fragments produce well synchronized peaks o f ecdysterone and this does not depend on the PG. It thus appears that some thoracic tissue other than PG is able to maintain the physiological concentration o f ecdysterone by means o f a concentration-dependent feed-back mechanism. Due to spontaneous metamorphosis and extremely good survival we have succeeded to induce in this species: a) premature formation o f the prepupal cycle of ecdysterone synthesis in the penultimate larval instar by ligation; b) inhibition and delay o f the prepupal peak by means of juvenoid treatments; c) reappearance o f the prepupal peak in the inhibited "permanent larvae" by exogenous administration of ecdysterone, or; d) modification of the pupal peak by a qualitatively new pupal-pupal one after juvenoid treatments. These experimental transformations o f the ecdysterone peaks have suggested that the kind and nature o f the peaks are closely related to nature and stage o f the ontogenetic development. We therefore believe that the process o f larval-pupal reprogramming has occurred in this species long before the increase o f ecdysterone titer in the body. Both the prepupal and pupal peaks do not represent a cause but they show to be rather consequences o f the developmental programming. Further features associated with possible physiological role o f ecdysteroids in insect development have been briefly discussed. | | | |
Reference
| Z. Naturforsch. 35c, 1066—1080 (1980); received June 19 1980 | | | |
Published
| 1980 | | | |
Keywords
| Ecdysteroids, Juvenile Hormone, Metamorphosis, Dermestes maculatus | | | |
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| default:Reihe_C/35/ZNC-1980-35c-1066.pdf | | | | Identifier
| ZNC-1980-35c-1066 | | | | Volume
| 35 | |
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