. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 52 JOHN H. POSTLEHWAIT AND HOWARD A. SCHNEIDERMAN. FIGURE 2. Eversion of the imaginal leg disc induced by ecdysterone ; (A) Ninety-six lir. imaginal leg disc; (B) Five-hr pupal disc, note eversion; (C) Control discs, 24 hrs after treat- ment with control solution; (D) Leg disc 24 hrs after treatment with 120 /*g/g ecdysterone; (E) Control disc 24 hrs after treatment with control solution; (F) Leg disc 24 hrs after treat- ment with 1200 fj-g/g ecdysterone (photograph (B) was taken by C. A. Poodry). have found that in Callipho
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 52 JOHN H. POSTLEHWAIT AND HOWARD A. SCHNEIDERMAN. FIGURE 2. Eversion of the imaginal leg disc induced by ecdysterone ; (A) Ninety-six lir. imaginal leg disc; (B) Five-hr pupal disc, note eversion; (C) Control discs, 24 hrs after treat- ment with control solution; (D) Leg disc 24 hrs after treatment with 120 /*g/g ecdysterone; (E) Control disc 24 hrs after treatment with control solution; (F) Leg disc 24 hrs after treat- ment with 1200 fj-g/g ecdysterone (photograph (B) was taken by C. A. Poodry). have found that in Calliphora its inactivation is due to an enzyme system present in the fat body. Since ecdysterone is probably also degraded in adult Drosophila, and repeated small doses are more effective in inducing metamorphosis than single large doses, we conclude that ecdysterone is necessary as a sustained stimulus, and not merely as a trigger to metamorphosis. In silkmoths, a high dose (10 /*g/g) of ecdysterone causes pupal-adult inter- mediates (Kobayashi, Takemoto, Ogawa and Nishimoto, 1967; Williams, 1968; Madhavan and Schneiderman, personal communication). Diptera, however, such as Afiisca larvae treated with a high dose of ecdysterone (300 ju-g/g) (Kobayashi, ct 1%7) and Drosophila imaginal discs treated with a very high dose of ecdysterone (3600 /*g/g) show no such abnormalities. This may be due to rapid inactivation of ecdysterone in Diptera (Ohtaki ct al., 1968), or a difference in threshold response to the hormone. The adult corpus allatum of flies continues to secrete juvenile hormone (Wigglesworth, 1954), which probably is the same factor as the yolk-forming hor- mone (Wigglesworth, 1948). Traditional explanations of hormonal control of insect development (Schneiderman and Gilbert, 1964) would predict that a given low level of juvenile hormone might permit deposition of pupal cuticle, and the absence of juvenile hormone would allow adult cuticle to be formed. The present experime
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
