Growth rate and life span in Drosophila. III. Effect of body size and developmental temperature on the biphasic relationship between growth rate and life span.

The previous finding of a biphasic relationship between life span and growth rate of Drosophila, developed at 25 degrees C, was confirmed at other temperatures in the usual range (19-28 degrees C) and for development in either a standard medium or one deprived of nutrients but with varying amounts of yeast added on the medium. The role of body size in this relationship was studied by developing flies in a nutrient-less medium with a constant, submaximal amount of added yeast and varying temperature. It was found that under these conditions, which abolished the usual inverse relationship between body size and developmental temperature, body size variations did not account for the observed variations in life span. Thus, corroborating previous studies from this laboratory, body size was ruled out as a causative factor in the life span-growth rate relationship.