Adaptation of Drosophila melanogaster under the Constant and Fluctuating Temperatures

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1) Two experimental populations were made each with about 1, 000 F2 flies of 192 female flies collected from natural populations of Drosophila melanogaster at Kofu and Katsunuma in Yamanashi Prefecture. One population (F population) has been maintained in a population cage in the incubator "KOITOTRON", in which the temperature was regulated by a program controller so that it fluctuated two times a day between 20 and 30°C (f environment) . The other population (C population) has been maintained in a population cage in the culture room, in which the temperature was kept constant at 25°C (c environment) . These two populations have been maintained for about two years and flies used in the experiment were sampled from them randomly. 2) Flies sampled from C population were exposed toc environment (C-c group) and to f environment (C-f group), and flies sampled from F population were exposed to f environment (F-f group) and to c environment (F-c group) . Longevity of female flies (Exp. I), fecundity (Exp. II, III) and egg to adult hatchability (Exp. IV, V, VI) were estimated under constant and fluctuating temperatures and the results for the four groups were compared. 3) The mean longevity of female flies in F-f group was 31.3 days and that in C-c group was 29.0 days. The longevity in constant environment was generally shorter than in fluctuating environment, but the mean longevity of female flies in F-c group was remarkably short being 25.7 days. 4) Fecundity and longevity are closely related quantitative characters. Mean longevity of female flies in constant environment was shorter, but their mean fecundity was superior to that of female flies in fluctuating environment. Especially, young female flies (until 10 days after emergence) in C-c group laid significantly more eggs than in C-f group. However, the total number of eggs laid by female flies during 40 days in F-c group which showed the shortest mean longevity, was smaller than in other groups. 5) Egg to adult hatchabilities of young 1-10 days old female flies of the four groups were higher than 90 per cent and no difference was found between them. However, the hatchability of C-c group decreased faster than in other groups with the age of female flies advancing to 15 and 20 days, and that of 20 days old female flies was 61-67 per cent. On the other hand, the hatchability of 20 days old female flies of F-f group was kept at 71-81 percent and those of the other two C-f, F-c groups were almost intermediate. 6) Longevity, fecundity and hatchability are thought to be important components of fitness in Drosophila. These quantitative characters are controlled by polygenes. When the variances in these characters of the four groups were calculated and compared with each other, homeostatic gene systems of flies in F and C populations cultured under fluctuating and constant temperatures were revealed and the grade of homeostasis of the former was. considerably higher than the latter. Especially, the manifestations of these characters in F population were very unstable and widely fluctuating under constant temperature and the cause of the result was discussed.
日本生物環境工学会の論文

Adaptation of <I>Drosophila melanogaster</I> under the Constant and Fluctuating Temperatures

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日本生物環境工学会 | 論文

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