A search for principles of disability using experimental impairment of Drosophila melanogaster

Abstract

The results of life table experiments to determine the effects of artificial impairment (leg amputation) in 7,500 D. melanogaster adults revealed that the extent to which life expectancy was reduced in impaired individuals was conditional on: (1) leg location and number amputated-front leg had greatest impact and the number of legs amputated directly correlated with mortality impact; (2) age of amputation-the greatest relative reduction in remaining life expectancy occurred when young flies were impaired; (3) vial orientation-mortality in impaired flies was the least when vials held upside-down (most friendly environment) and the greatest when they were right-side up (least friendly environment); and (4) sex-male mortality was reduced more than female mortality in nearly all impairment treatments. These results were used to formulate a set of general principles of disability that would apply not only to humans but to all organisms.

Interactions between injury, stress resistance, reproduction, and aging in Drosophila melanogaster

“…These results partially corroborate Carey et al (2007), who found a stronger effect of injury on males than on females. However, we recorded mortality rates, while Carey et al (2007) recorded life expectancies, so the results are not directly comparable. Injury did not affect the rate of aging (i.e.…”

“…However, these procedures resulted in acute effects on mortality, in that the flies died within the first few days, and sometimes within only the first few hours. We avoided removal of the front legs, which is a procedure that Carey et al (2007) included in their study, because of the role of the front legs in mating: males use the sex combs on their front legs to mount the female. We also avoided removal of the back legs in order to avoid a radical effect on the mobility of the injured flies.…”

“…An important aspect of the aging process in insects is the accumulation of injuries that lead to loss of physical function (Burkhard et al, 2002;Carey, 2003;Carey et al, 2007;Finch, 1990;Hayes and Wall, 1999). In the laboratory fruit fly, Drosophila melanogaster, these injuries include the loss of antennae, legs, bristles, and parts of wings with age (Burkhard et al, 2002), leading to a loss of hemolymph, which contains water and nutrients that may be essential to a fly's survival (Folk et al, 2001).…”

“…In a study of the effects of induced injury to D. melanogaster, Carey et al (2007) saw a decrease in life expectancy in deliberately injured flies, suggesting that the losses incurred via injury have a survival cost. Given these results, it is conceivable that reductions in available water and nutrients as a result of injury to the exoskeleton of insects might decrease resistance to starvation and desiccation stresses, and thereby negatively affect survival.…”

Species, age and sex differences in type and frequencies of injuries and impairments among four arboreal primate species in Kibale National Park, Uganda

“…In primates, reported impairments include birth defects (Schultz 1956;Iwanoto 1967;Turner et al 2005), consequences of diseases like arthritis (Jurmain 2000;Nakai 2003) or aging (Randall 1944;Schultz 1944), as well as the results of injuries that are inflicted by external agents and accidents (Jurmain 1989(Jurmain , 1997Lovell 1990). Only when impairments hamper essential activities do they cause disability (Byrne and Stokes 2002;Carey et al 2007). …”