Life Span in <i>Drosophil</i><i>a</i>

Abstract

Recent experimental evidence does not coincide with the predictions of the different theories of ageing in Drosophila. A review of the evidence and more specifically of the experimental methods in use shows that in experiments one or more variables have in general not been taken into account. These variables are of different types; their influence on imaginal life span may be direct or indirect; direct through the action of con-temporaneous environmental factors, indirect through the action of parental or of antecedent environmental factors. An alternative theory of ageing is proposed; it essentially relates imaginal life span in Drosophila to the preimaginal rate of growth.

THE LANSING EFFECT REVISITED. II.-CUMULATIVE AND SPONTANEOUSLY REVERSIBLE PARENTAL AGE EFFECTS ON FECUNDITY INDROSOPHILA MELANOGASTER

“…It is well known in Drosophila that both life span and fecundity are extremely sensitive to a great variety of direct environmental factors such as temperature, light regimen, population density, presence or absence of the other sex and so on (for a review, see Lints, 1971 Maximal daily egg production 89.0 ± 4.3 113.6 ± 6.0 10.6** c ns; * 0.05 < P < 0.10; ** 0.01 < P < 0.05; *** 0.001 < P < 0.01; **** P < 0.001.…”

“…the preimaginal temperature and population density which affects the imaginal life to a considerable extent (Lints andLints, 1969, 1971). Therefore the following procedure was used throughout.…”

“…Accordingly, the younger the flies, the higher the egg, larval and pupal density. The preimaginal population density affects the imaginal longevity to a considerable extent; it also affects, although to a lesser extent, the imaginal fecundity and the viability of the eggs (Lints andLints, 1969, 1971). David (1961) measured the fecundity of different lines reproduced during some generations by means of parents aged three weeks.…”

Life-Span of Mosquitoes (Culicidae, Diptera) under Laboratory Conditions

“…It should be pointed out that in all these experiments, besides the contempora neous, the antecedent environmental factors were also kept constant and identical to a large extent, as was called for by Lints [1971]. Parents of all the experi mental animals have been bred for generations under the same climatic conditions as the experiments were done.…”

The Effect of Lowered Body Temperature on Lifespan and Immune and Non-Immune Processes

“…Thus, the fruit flies' lifespan may be divided into two phases: 'ageing or induction', and 'dying or development' [MaynardSmith, 1962], The dying phase cannot only be stretched out but may also in a sense be reversed by temperature manipulation (intermittent hy pothermia), since flies kept alternately at high and low temperatures (1 day at 30 °C, 3 days at 20 °C) live almost as long as those kept contin uously at 20 °C. Other workers relate longevity in Drosophila to the temperature during development [Burcombe and H ollingsworth, 1970;Lints, 1971; Lints and Lints, 1971]. Vertebrates Among other than comparative physiologists and ecologists the no tion seems to exist that all poikilothermic vertebrates are quite unable to control body temperature and that homeothermic vertebrates are able to do so to a precise degree.…”