Simultaneous bagging on 15 plates, N2 and 3 other strains

Last week, I set up fifteen 35-mm NGM/OP50 plates with small chunks
containing my various strains of worms*. I incubated them at 20C, the
proper temperature for all my strains**. Friday afternoon, all the
plates seemed to be full of healthy adults, various larvae, and oodles
of eggs. Friday evening, they were all full of bagged adults, various
larvae, and newly hatched L1s. So they must have stopped laying eggs
quite some time earlier.

Both my control and heat shock worms were bagging. My treatment worms
were heat-shocked for 2 hours at 33C on a heating block with a lid over
it, while controls stayed in the 20C incubator. I started picking
control worms for microscopy 5 hours after my pre-experiment check,
followed by experimental worms about 7.5 hours after the initial
checking. The heat shock worms were a bit worse, which could reflect
being examined later and having a faster metabolism for a couple of
hours.

What would cause them to suddenly fail to lay eggs?

None of the plates were starved; depending on the population, most of
the plates had at least adequate food and most had a substantial lawn.
The worms were merrily chowing down on OP50 until they died from being
full of larvae. I've been raising N2s and CL2070s for about a year, and
I've never seen anything like this. (The other strains, CL2122 and
CL2166, are new to my lab, but seem to have similar development to N2
now that I've switched to Difco agar and glass-distilled water. They
have GFP reporters for mtl-2 and gst-4.)

**We had some trouble with the incubator Friday evening (power surge
that tripped a breaker, not discovered until a few hours later) but
bagging takes more than a couple of hours, right?. Our power is pretty
"dirty" here at a rural college, and whenever we have windy weather, we
get power drops and surges. Could an incubator respond to that kind of
abuse in some way that would affect egg-laying? Heat spikes, cold
spells, electromagnetic phenomena?

*The plates were poured 10/31/06, seeded with OP50 on 11/1/06, and
chunked from 5-day-old unsynchronized plates on 11/7/06. By 10/10/06,
they had substantial but not overcrowded populations and adults had
been laying eggs prolifically.

If anyone else has experienced sudden failure in egg laying, I'd like
to hear from you. (Especially if you know how to prevent it from recurring.)

Sincerely,

Kathryn Hedges
Graduate Student, Biology
Humboldt State University
1 Harpst St., Arcata, CA 95521
619-602-9839 cell