Aa. Khazaeli et al., EFFECT OF ADULT COHORT DENSITY ON AGE-SPECIFIC MORTALITY IN DROSOPHILA-MELANOGASTER, The journals of gerontology. Series A, Biological sciences and medical sciences, 50(5), 1995, pp. 262-269
Mortality rates decelerate at older ages in experimental populations o
f Drosophila. It is unclear whether this reflects a real slow-down in
the aging process, or an artifact of declining density. Mortality was
studied in age-synchronized cohorts of four inbred lines at three init
ial densities that varied 10-fold. A total of 70,000 flies of both sex
es were studied. There were large line x density, line, and sex effect
s, but no systematic relationship between density and life span was de
tected. Mortality curves level off at older ages in 23 out of 24 sex-g
enotype combinations, irrespective of initial cohort density. Density
has only second-order effects on the pattern of oldest-old mortality o
ver the range of densities studied here. The dramatic departure from G
ompertz-type mortality dynamics at older ages is not an artifact of de
clining density in Drosophila.