X-Message-Number: 27213
Date: Fri, 14 Oct 2005 11:53:54 -0700 (PDT)
From: Doug Skrecky <>
Subject: 200'th update on fly longevity experiments

     This is the 200'th update of my fly longevity experiments. Average
 temperature was 27.8 C during this run. Estimated maximal longevity using
 the formula (363 - T*11.2) is 52 days.
     I'd originally planned on having a large run testing all the "best"
 supplements for the 200'th "birthday" of my fly longevity experiments.
 Alas, due to an oversight I'd let the breeding bottles get a little too
 old, and the large numbers of (healthy) flies required were simply not
 available. Instead I decided to test once again the effect of citric
 acid, and in addition check out the preservative potassium sorbate, which
 is effective at killing bacteria, as well as molds.
     Probably due to the fact that I now use only "fresh" fly food, there
 was once again no advantage for citric acid additions. Considering the
 wide use of potassium sorbate in human foods, the toxicity detected in
 this run gives one pause for consideration. I conclude that any
 hypothetical pathogens that may be growing on the fly food itself are
 likely not harming the flies. However I do still think pathogens probably
 were a major limiting factor, and likely accounted for the maximum
 longevity of just 29 days in this experiment. I attribute the early
 deaths to direct fly to fly contact. The use of "old" breeding bottles is
 strongly suspected of increasing the pathogen load in flies.

 Run #200        Percent Survival on Day
 supplement           10 17 23 29 35
 ___________________________________
 control              77 54 39  0  -
 K sorbate 1/8 tsp    55 41  0  -  -
 K sorbate 1/4 tsp    56  6  6  0  -
 citric acid 1/8 tsp  53 27 13  7  0
  + K sorbate 1/8 tsp 24  0  -  -  -
  + K sorbate 1/4 tsp 17  0  -  -  -
 citric acid 1/4 tsp  32 11  5  5  0
  + K sorbate 1/8 tsp  0  -  -  -  -
  + K sorbate 1/4 tsp  0  -  -  -  -

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