flesh fly larva article

flesh fly larva article - J Insect Physiol,1973 Vol 19 pp...

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J. Insect Physiol., 1973, Vol. 19, pp, 1941 to 1954. Pergamm Press. Printed in Great Britain THE PHOTOPERIODIC CLOCK IN THE FLESH-FLY, SARCOPHAGA ARGYROSTOMA D. S. SAUNDERS Department of Biological Sciences, Stanford University, Stanford, California, U.S.A.; and Department of Zoology, University of Edinburgh, Scotland (Received 26 March 1973) Abstract-Larval cultures of the flesh-fly, sarcophaga argyrostoma, were raised in experimental light cycles with periods (T) of 21 to 72 hr, each cycle containing a photoperiod of 4 to 20 hr of white light. This ‘resonance’ technique revealed periodic maxima (N 24 hr apart) of pupal diapause, thereby demon- strating an endogenous circadian component in the photoperiodic clock. The positions of these maxima of pupal diapause suggested that the oscillation, like that controlling the pupal eclosion rhythm in Drosqphika pseudoobsctwa, is ‘damped out’ by photoperiods longer than about 11 to 12 hr, but restarta at dusk whereupon it runs with circadian periodicity in a protracted dark period. With photoperiods shorter than 12 hr, however, the two diapause maxima were less than 24 hr apart, suggesting that an additional component, possibly a ‘dawn hour-glass’, was modifying the position of the first peak. Both photoperiod and the period of the driving light cycle (T) were shown to affect the length of larval development (the sensitive period) and the number of calendar days needed to raise the incidence of pupal diapause to 50 per cent (the required day number, RDN). Peaks of diapause induction were shown to be the result of an interaction between a long sensitive period (slow develop- ment) and a low RDN, whereas troughs in diapause induction were the result of an interaction between a short sensitive period (fast development) and a higher RDN. Larvae of S. argyrostonua are unable to distinguish (in a photoperiodic sense) between 12 and 18 hr of red light ( > 600 nm). INTRODUCTION LARVAE of the flesh-fly, Surcophaga argyrostoma, maintained at short daylength enter diapause as pupae whereas those kept at long daylength develop without arrest (FRAENKEL and HSIAO, 1968). DENLINGER (1972) has since demonstrated that the intra-uterine embryos of Smcophagu spp. are particularly sensitive to photoperiod. Working with a northern European strain of S. argyrostoma, SAUNDERS (1971) showed that the ‘sensitive period’ effectively came to an end at puparium formation. During this period the larvae ‘add up’ successive short-day cycles and enter diapause (as pupae) if a sufficient number of such signals have been seen before the end of the sensitive period. Although the length of larval development (the sensitive period) was temperature dependent (Q1,, = 2.7) the number of short-day cycles needed to programme the insects for subsequent diapause (the required day 1941
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1942 D. S.
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flesh fly larva article - J Insect Physiol,1973 Vol 19 pp...

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