Growth rate and life span in Drosophila. I. Methods and mechanisms of variation of growth rate.

It has been suggested that development and ageing may be linked and it has been shown, in Drosophila, under conditions of varying developmental temperature and larval crowding that the rate of development may be inversely related with the duration of adult life. In order to test this hypothesis systematically, precise methods were devised for varying, in Drosophila, either growth rate or each of its components, i.e. body weight and duration of development, while holding the other constant. These methods are described in the present paper. Moreover, we report studies that shed some light on the mechanisms underlying the effects of temperature and larval crowding on Drosophila development. The major novel findings from these studies were: (a) the restriction of the amount of yeast per larva as larval density increases accounts entirely for the effect of larval crowding on duration of development but only for about two-thirds of its effect on body size; and (b) the increased size of flies grown at lower temperatures may be due to assimilation of more food rather than to more efficient assimilation of food.