From: Doug Skrecky (oberon@vcn.bc.ca)
Date: Sun Dec 22 2002 - 10:56:37 MST
This is the 75'th update of my fly longevity experiments. Average
temperature was 25.5 C during this run. Here I examine the effect of fly
population size on survival, and its (possible) interaction with taurine
dosage. Please note that I usually add 1 gram of taurine to 20 grams of
4-24 fly food per bottle, to act as a nontoxic larvicide.
As it turned out, taurine dosage had no consistent effect on
longevity, so the results for this run are listed below, in fly number
order. In theory one might anticipate three population effects. Maximum
lifespan should be increased, if more flies are used, since extremely old
flies are expected to be few and far between. On the other hand a high
population density might promote the transmission of pathogens between
flies, and so average longevity would then be reduced if the population is
too high. Another negative effect from too high a population would be
increased mating frequency, which would also act to reduce average
longevity.
From the data presented below it appears average longevity (see day
21) is increased if fly number is below about 20 flies. Maximal longevity
displays a bimodal distribution, with fly numbers either below 10, or
above 30 showing some advantage. I generally try to place between 15 and
30 flies in most of my runs. However due to the limited number of flies
available from a single breeding bottle, increasing this number is not
feasible. On the other hand, I'm uncomfortable statistically with reducing
fly number to less than 10 per bottle. I'll have to try this experiment
again, in the future, to see how robust this less-than-10-fly effect is.
Run #75 No of Percent Survival on Day
supplement Flies 9 16 21 26 32 39 44 51 56 63
___________________________________________________________
taurine 1/2 gm 54 78 50 43 26 15 9 6 2 2 0
taurine 1 gm 54 70 44 31 19 13 4 4 4 0 -
taurine 1/2 gm 33 73 55 45 33 15 9 9 3 0 -
taurine 1 gm 24 54 29 29 25 13 8 4 0 - -
taurine 1/2 gm 15 87 87 67 47 27 0 - - - -
taurine 1 gm 11 73 73 64 27 27 9 0 - - -
taurine 1/2 gm 9 89 89 67 56 44 11 11 11 0 -
taurine 1 gm 6 100 67 50 50 50 33 33 33 0 -
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