Drosophila Fruit Flies

The fruit fly, Drosophila melanogaster, has been a leading model for aging research since early in the twentieth century. The benefits of using D. melanogaster for research include its short life span (1 to 2 months), ease of culture, and the availability of powerful genetic and molecular biological tools. The latter includes the Drosophila "P element," which is a transposable element. Transposable elements are pieces of DNA that can insert into the DNA of a chromosome, and can move from one place in the DNA to another under appropriate conditions. The P element has been engineered so that scientists can control its movement in D. melanogaster. For example, it can be used to carry modified or foreign genes into the D. melanogaster genome, where they will then be inherited by succeeding generations. Such introduced genes are called transgenes, and the resultant strain is said to be transgenic. One disadvantage of D. melanogaster for aging research is that its small size precludes detailed study of pathology and cause of death. For this reason, life span is still the most reliable measure of the D. melanogaster aging rate.

The use of D. melanogaster as a model is supported by the numerous similarities between aging in fruit flies and mammals, including a decline in performance of functions such as reproduction, learning, behavior, and locomotion. At the ultrastructural level, similarities include deterioration of muscle and nervous tissue, as well as accumulation of intracellular inclusions such as pigments (lipofuscin), abnormal mitochondria, A close-up view of the Mediterranean fruit fly. (Corbis Corporation) and virus-like particles. At the molecular level, similarities include the accumulation of damaged DNA, proteins, and mitochondria. Finally, both fruit flies and mammals exhibit a tight link between stress responses and aging.

An important difference between D. melanogaster and mammals is the fact that fruit flies are cold-blooded. Raising the environmental temperature increases the rate of D. melanogaster metabolism and aging, and decreases its life span. The ability to manipulate life span in this way has proven to be useful in many studies, and has provided some the first evidence of a link between metabolic activity and life span.