Stress Does Appear to Accelerate Aging At Least in
Males
Both sexes found to live shorter lives in stressful
environment
A marked T.
angusticollis female on an Acacia trunk in Sydney. Photo: N.
Kawasaki
Sept. 5, 2008 Most of us assume that stress
causes us to age faster, but the attempts to measure this in laboratory
conditions may not provide the best results. Some enterprising
researchers decided to take this test to the wilds.
Studies of aging typically use small, short-lived
creatures, like insects, worms and mice. The studies also customarily
take place in a laboratory with a pleasant environment constant
temperature and humidity, no parasites, very abundant food supply,
plenty of water, etc.
Oddly enough, very little is known about aging in
such animals in their harsh, stressful natural environments. Could it be
that these laboratory "guinea pigs" actually age much more slowly in
captive luxury than do their wild cousins?
These scientist decided it would be interesting to
see how these creatures aged, if left to face the stressful challenges
of their natural environments.
Nori Kawasaki, Rob Brooks, and Russell Bonduriansky
of the University of New South Wales, and Chad Brassil of the University
of Nebraska, set out to find out, using the giant Australian
stilt-legged fly Telostylinus angusticollis, a beautiful animal that
breeds on rotten wood.
To identify individual flies in the wild, they
wrote codes (combinations of Arabic numerals and Latin and Japanese
letters) on the flies' backs using enamel paint, and recorded the
comings and goings of marked individuals on Acacia trunks while
simultaneously monitoring their captive cousins in the lab.
Analysis, published in the September issue of the
American Naturalist, revealed striking contrasts between wild and
captivity.
● Males live less than one-fifth as long and age
at least twice as rapidly in the wild as do their captive counterparts.
● Curiously, they found no evidence of aging in
wild females.
● But, for both sexes, life expectancies in the
wild were dramatically shorter than in the lab.
These striking sex-specific differences between
captive and wild flies support the emerging view that environment exerts
a profound influence on the expression of life span and aging, the
authors conclude in their report in the current issue of American
Naturalist.
Evolutionary biologists have long sought to
understand how environmental factors generate natural selection on the
rate of aging, and ultimately influence the frequencies of genes that
underpin genetic variation in this trait. Much less is known about how
environment affects the expression of genes that modulate aging rate.
This study has shown that animals can age much
faster in their stressful natural environments than in the benign
conditions of the laboratory. Their results suggest that laboratory
estimates of aging and lifespan (and, therefore, fitness) should be
interpreted with considerable caution.
Reference:
Noriyoshi Kawasaki, Chad E. Brassil, Robert C.
Brooks, and Russell Bonduriansky, "Environmental Effects on the
Expression of Life Span and Aging: An Extreme Contrast between Wild and
Captive Cohorts of Telostylinus angusticollis (Diptera: Neriidae)"
American Naturalist (2008) 172:346-357.
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