X-Message-Number: 25663
Date: Sat, 5 Feb 2005 11:53:03 -0800 (PST)
From: Doug Skrecky <>
Subject: 165'th update on fly longevity experiments
This is the 165'th update of my fly longevity experiments. Average
temperature was 21.4 C during this run. Estimated maximal longevity using
the formula (363 - T*11.2) is 124 days.
This run investigates the effect of adding citric acid to both the
breeding bottles, as well as bottles in the run itself. The breeding
bottles with either zero or 1/4 tsp citric acid were a closely matched
pair, from the same source bottle, and having the same creation date. The
breeding bottle with 1/2 tsp citric acid was a slightly older bottle,
with a different source. This higher level of acid blocked larval
development, until some extra water was added to reduce this toxicity.
The results explain the inconsistancies with citric acid addition to
runs in the past. In order to boost maximum longevity citric acid has to
be present in both the breed, as well as the run bottle. As expected a
toxic 1/2 tsp dose prevented the emergence of extremely old flies. Please
note that the flies provided by my breeding bottles are of random ages,
and so some significant mortality has to be expected early in the run,
due to the presence of already old flies.
This run sets a new longevity record of 137 days, which exceeds the
previous record of 134 days set in run #164. Although 137 days exceeds
the estimated maximum longevity of 124 days for the current run by 10%,
this estimate is based on "professional" experiments that did not add
citric acid to both breeding and run bottles. As far as I am aware this
has never been attempted before.
One rationale for the addition of citric acid has been to restrict
bacterial growth, but I doubt that this explanation is sufficient to
explain the large increases in maximum longevity obtained. Acid addition
may also be inhibiting the frequency of breeding, which is known to
involve the exchange of toxins. As can be seen, joint addition of
citric acid to both the breed and run bottles increased maximum
longevity in the present experiment by up to 52%.
Run #165 Percent Survival on Day
breed bottle run bottle 62 70 80 90 100 108 117 122 124 133 134 137 138
_______________________________________________________________________
citric 0 0 tsp 35 26 17 9 0 - - - - - - - -
citric 0 0 23 14 9 9 0 - - - - - - - -
citric 1/4 0 34 34 20 7 5 2 0 - - - - - -
citric 1/4 0 29 18 5 5 3 0 - - - - - - -
citric 1/2 0 35 23 10 8 4 0 - - - - - - -
citric 1/2 0 36 29 11 4 2 2 2 2 0 - - - -
citric 0 1/8 73 55 41 18 5 0 - - - - - - -
citric 0 1/8 35 28 10 7 0 - - - - - - - -
citric 1/4 1/8 67 55 45 33 19 12 12 10 5 2 0 - -
citric 1/4 1/8 66 63 47 41 31 16 13 13 13 6 3 3 0
citric 1/2 1/8 40 40 25 20 8 5 3 0 - - - - -
citric 1/2 1/8 28 25 13 9 6 6 6 0 - - - - -
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