Developmental temperature and life span in Drosophila melanogaster. II. Oscillating temperature.

Alternating developmental temperature within the viable range 13-33 degrees C, with increasing amplitude around a mean value of 23 degrees C but constant period (2 days, a 1 day/1 day rhythm), resulted in increased duration of development, decreased body weight and decreased growth rate of both male and female flies. Life span of female flies also decreased with increasing amplitude of temperature of oscillation but that of males increased (compared to that at the mean temperature) at moderate temperature amplitude. Variation of the period of oscillation (from a rhythm of 6 h/6 h up to 2 days/2 days) with constant amplitude (23 +/- 5 degrees C), on the other hand, did not affect either duration of development or body weight of the flies. However, life span of the females only was unaffected but that of males was increased (above that at mean constant temperature 23 degrees C) at the fast oscillation patterns (6 h/6 h and 1 day/1 day). Finally, life span of both sexes was positively correlated with growth rate in the constant period/varying amplitude case, whereas in previous studies variation of growth rate in the same range by other means showed a biphasic or an invariant pattern of life span dependence on growth rate. These results are in agreement with the hypothesis of epigenetic influence on life span by alternating developmental temperature and corroborate the previous conclusion that growth rate per se does not determine life span.