| Budget Amount *help |
¥5,600,000 (Direct Cost: ¥5,600,000)
Fiscal Year 1990: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1989: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1988: ¥3,800,000 (Direct Cost: ¥3,800,000)
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| Research Abstract |
The physiological traits involved in the seapsonal adaptation of insects are highly variable. Oxya yezoensis showed geographic variations in duration of the larval stage and adult size, both correlated with the unmber of moults. The latter was genetically variable and photoperiodically modified. Adults were normally winged nuder long days, but brachypterous under short days. In Dianemobius fascipes, the frequency of macropterous adults could be either increased of decreased by selection through 30 generations. However, there was no diffserence in the pattern and threshold of the photoperiodic response between the predominantly macropterous. and micropterous lines. Hybrids between the two lines indicated that the frequency to macropterous abults was controlled by a polygenic system and that at least one sexchromosomal locus was involved. In this subtropical species, the incidence and intensity of egg diapause were highly variable. We selected for incubation periods of <20, 50-60, 100-11
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0, and >150 days over 5-20 successive generations at 25'C and LD 12 : 12. The mode of the incubation period was proportional to the selection goal. Therefore, the incidence and intensity of egg diapause seem to be controlled by a polygenic system. Some eggs in the <150-day line had an intensity of diapause comparable to that in the related temperate species, suggesting a subtropical origin of the stabilized temperate diapause. A subtropical diapause was confirmed also in abults of euconocephalus spp. In Mamestra brassicae expression of the time-measuring mechanism underlying the photoperiodic response was variavle. When larvae were subjected to photoperiodic cycles with various periods at 20'C, no resonance effect was detected, suggesting the involvement of an hour-glass mechanism in the photoperiodic response. However, similar experiments at 22 and 24'C gave responses with circadian rhythmicity. The involvement of circadian rhythmicity was confirmed by analyzing entrainment effect on the photoperiodic time measurement. Less
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