Studies in ageing—VIII hormonal concentration and homeostatic adjustment in Drosophila

Abstract

The physiological effects of altering the hormonal concentration in Drosophila melanogaster were studied. Hosts and donors consisted of the Swedish-b 8 inbred females. The experiments were performed in a series asynchronously. In one series, corpus-allatum complexes from freshly emerged donors were transplanted individually into 10-day-old females; in another series, one ring gland from 80 to 85 hr old larvae was injected into each 14-day-old host; in still another series, experiments similar to the previous series were performed, except that hosts were injected with ring glands on the 3rd day of adult life. Controls were made by injecting approximately 0·001 μl of Ringer's solution into individual females synchronously with hosts in a series. The adult life span and egg production of the experimental and control populations were measured at 25 ± 0·50°C. No differences were observed in the adult longevity or fecundity of hosts receiving injections of corpus-allatum complexes, whereas transplantations of ring glands into younger and older females produced a life-shortening effect without a change in the fecundity. The deleterious effects observed in hosts are explained as due to an increase in the concentration of ecdyson which interferes with the normal metabolic processes. The reduced life span and unaffected egg production in females are considered in terms of homeostatic mechanisms which insure the period of normal reproduction. It is suggested that the kind of flexibility observed in the present experiments is generally retained by living systems and that therefore it is possible to improve the physiology of organisms by interfering with them.