Hour-Glass Behavior of the Circadian Clock Controlling Eclosion of the Silkmoth Antheraea pernyi
AUTOR(ES)
Truman, James W.
RESUMO
The emergence of the Pernyi silkmoth from the pupal exuviae is dictated by a brain-centered, photosensitive clock. In continuous darkness the clock displays a persistent free-running rhythm. In photoperiod regimens the interaction of the clock with the daily lightdark cycle produces a characteristic time of eclosion. But, in the majority of regimens (from 23L:1D to 4L:20D), the eclosion clock undergoes a discontinuous “hourglass” behavior. Thus, during each daily cycle, the onset of darkness initiates a free-running cycle of the clock. The next “lights-on” interrupts this cycle and the clock comes to a stop late in the photophase. The moment when the Pernyi clock stops signals the release of an eclosion-stimulating hormone and is demonstrated to be a function of the time when the free-running cycle is interrupted by lights-on. Moreover, the width (duration) of the eclosion peak in a photoperiod is shown to be dependent upon the length of the dark phase, and, consequently, upon the amount of the free-running cycle that is completed. This relationship demonstrates that the free-running cycle may be divided into two parts. The attainment of maximal accuracy (and thus the narrowest eclosion peak) is dependent upon the completion of only the first 2 hr of the free-running cycle. The completion of succeeding portions of the cycle, while having an effect upon the time of eclosion, no longer affects the accuracy of the clock. A mechanistic model of the eclosion clock is presented.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=388997Documentos Relacionados
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