X-Message-Number: 22229
Date: Sat, 19 Jul 2003 13:22:20 -0700 (PDT)
From: Doug Skrecky <>
Subject: 95'th update on fly longevity experiments
This is the 95'th update of my fly longevity experiments. Average
temperature was 21.0 C during this run. Estimated maximal longevity using
the formula (363 - T*11.2) is 128 days.
Here I examine the effect of breeding bottle age on mortality. When
older bottles are used as a source of flies, I've noticed mortality tends
to be higher. This could be due solely to the fact that there would tend
to be a greater percentage of old flies in an older bottle. However it
might also be partly due to increased viral load, which would also tend to
increase mortality rates.
To control for older flies, I vaccuumed one 37 day old breeding
bottle, and one 56 day old breeding bottle, 17 days before the start of
this experiment. All flies in these two bottles, therefore will be no more
than 17 days old at the start of this experiment.
A second 56 day old breeding bottle was left alone, so as to provide a
full range of fly ages. I suspect older flies are more diseased than
younger flies, so their retention may indirectly increase viral load in
the younger flies as well. If this is the case, then not only average
longevity in flies from this bottle would be reduced, but also maximum
longevity might also be reduced as increased viral load kills off the
younger flies a little earlier.
Under pathogen free "laboratory" conditions most flies live close to
their maximum lifespan, which is estimated at 128 days for this
experiment. My own experiments rarely see this limit being tested, due to
the fact that my flies are not pathogen free. Although late in some of my
experiments I do see some flies losing the ability to fly, due to
age-associated motor neuron degeneration, I believe the bulk of my flies
die from viral infections, rather than from cardio-respiratory arrest due
to extremely advanced age.
Three conditions are each tested three times each. First condition is
the breeding bottle being 37 days old, and being vaccuumed 17 days before
the experiment. Second condition is a 56 day old breeding bottle,
vaccuumed 17 days before the experiment. Finally the third condition is a
56 day old breeding bottle, used as is.
From the results from the current experiment I make three conclusions.
#1: Something besides extreme old age is killing off most flies in my
experiments. The oldest fly here could not be older than 98 days (17 days
+ 82 days -1). (I assume it is viral infections that account for this
reduced longevity.)
#2: Breeding bottle age has no significant effect on either average or
maximum longevity after the older flies are eliminated.
#3: Inclusion of older flies may increase mortality in younger flies,
which may sometimes result in a further reduced maximum lifespan.
It is ironic that except for those suffering from Huntington's disease
virtually no humans die from the motor neuron disease that ultimately
limits maximum fly longevity. Pathogen free flies do not provide a
appropriate model for age-associated human mortality. Conversely flies
exposed to viral infections do provide a model, as infections do account
for some deaths in aged human populations.
However it still would be very interesting to find some flies that
live beyond their estimated maximum lifespan, since not only would motor
neuron degeneration have to significantly delayed in these animals, but
resistance to illness would also have to be greatly increased. Thus far,
this has not happened in any of my experiments.
Run #95 Percent Survival on Day
supplement 11 16 21 26 32 38 44 49 54 60 66 71 76 82
____________________________________________________________________
<17 days (37 day bottle) 100 95 95 89 84 47 42 32 21 0 - - - -
<17 days (37 day bottle) 100 96 88 77 65 58 46 42 31 12 4 0 - -
<17 days (37 day bottle) 93 90 83 79 69 55 41 31 21 3 3 0 - -
<17 days (56 day bottle) 100 100 93 89 67 59 48 37 30 15 7 4 4 0
<17 days (56 day bottle) 96 92 79 75 67 58 54 50 46 37 17 0 - -
<17 days (56 day bottle) 91 91 83 78 74 70 52 48 30 13 0 - - -
56 day old bottle 85 85 60 55 35 25 20 15 5 0 - - - -
56 day old bottle 83 78 61 57 48 39 26 26 22 13 4 4 0 -
56 day old bottle 82 79 68 68 46 25 25 14 11 0 - - - -
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