[Drosophila] overseeding

Mark Thorson via dros%40net.bio.net (by nospam from sonic.net)
Wed Nov 14 19:55:27 EST 2012


I've noticed some of my cultures have a syndrome
I think is caused by seeding with too many adults.
The symptoms are many larvae, few pupae, and few
adults; unusually flat surface to the culture medium
aside from sort of a pebble grain texture; and most
of all, when light reflects off the surface of the
culture medium I can see the whole thing is alive
with motion.  It's that last one which makes me
suspect these cultures are suffering from larval
crowding.  Does that sound right, and if so, is
overseeding the cause?

For the past few days I've been careful to limit
the number of adults I use to about 20-25 per
culture.  I don't know what the optimal number is
for my culture system, but from experiments I did
several months ago I know there is no benefit from
using more than 30.  I have probably been using 
closer to 50, and I think the improvement in my
methods after adding calcium propionate has brought
out this new failure mode.  It'll be a week or two
before I know whether reducing the number of adults
used to start a culture eliminates the problem, but
even then I might not be sure because it is a
sporadic problem -- usually only a few cultures
are affected, though I did have one batch in which
all the cultures were affected.



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