X-Message-Number: 24368
Date: Sat, 10 Jul 2004 10:28:58 -0700 (PDT)
From: Doug Skrecky <>
Subject: 143'rd update on fly longevity experiments

    This is the 143'rd update of my fly longevity experiments. Average
temperature was 24.1 C during this run. Estimated maximal longevity using
the formula (363 - T*11.2) is 93 days.
    For some time, 1/8 tsp of citric has been a "standard" additive to
4-24 fly food, to help remedy a deficiency with respect to resistance to
bacteria. Some previous testing had indicated that higher dosages of
citric acid are more beneficial, and that sucrose additions are helpful as
well. Here I seek to determine what the optimal amounts of citric acid and
sucrose should be.
    Just how poor 4-24 fly food could be, took me by surprise. Although
this was an "older" batch of fly food I did not expect to see visible
"rotting" of the food in the no-additive, and 1 tsp sucrose bottles.
Fortunately neither the 2 tsp sucrose bottle, nor any of the bottles with
added citric acid showed such visible rotting.
    Although throughout most of the experiment the bottles with 1/2 tsp
citric acid were significantly superior, there was a late onset of mold in
these three bottles, which I believe destroyed the surviving flies. My
workbook blamed a bad batch of fly food.
    Naturally I would never consider using such a poor fly food, except
for two factors. 4-24 "medium" is the ONLY commercially available fly food
I have been able to import. My previous attempts to manufacture my own fly
food failed when I was refused access to a mold inhibitor, due to the lack
of certain letters after my name. For the forseeable future I will remain
stuck with 4-24 fly food, though I do plan on ordering it in smaller
batches. (Run #157 is taking a look at citric acid again, while using a
new batch of fly food.)
    Finally I have to account for the anomalously poor result for the 1/8
tsp citric bottle. This one is my fault. I use bleach to help clean out
old breeding bottles. My workbook listed that less care than usual was
spent washing two of these bottles.  The 1/8 tsp citric bottle likely
accounts for one of these, while the second bottle appears to have been
used in the next run. In future a more time consuming procedure will be
followed in my bottle washing.

Run #143                   Percent Survival on Day
supplement        11  16  23  28 37 43 48 53 58 70 79 85
________________________________________________________
none             100  97  87  62 35 27 19 11  3  3  0  -
citric 1/8 tsp   100  97   0   -  -  -  -  -  -  -  -  -
citric 1/2 tsp   100  97  94  90 84 77 74 55 23  0(mold)
sucrose 1 tsp    100  77  59  18  5  5  5  5  5  0  -  -
+ citric 1/8 tsp 100  95  95  79 47 42 21 16 11  5  0  -
+ citric 1/2 tsp 100 100 100 100 94 87 68 58 52  0(mold)
sucrose 2 tsp    100  91  82  77 62 38 29 18  3  3  0  -
+ citric 1/8 tsp  92  88  72  72 60 64 52 40 28 12  4  0
+ citric 1/2 tsp 100 100  97  97 94 88 78 66 41 13  0(mold)

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