Counting alive and dead worms

Dear All

I am looking for a method by which I can count alive and dead worms on a 60mm
Petri dish. From posts on this list my method so far involves putting the dish
in the fridge for about an hour, then placing it under a dissecting scope and
counting the worms as quickly as I can before they start moving again (to avoid
double counting). However, I need to distinguish which worms are alive and
which are dead. A colleague suggested that I poke them and if they move they
are alive, if not they're dead. Is there an easier way to do this - I wondered
for example if there was a stain that would be taken up by alive worms only?
Any suggestions much appreciated. For info - I have to do these counts many
times over, so any methods that would expedite this work would be welcome.

Best, Sarah

Dear Sarah,

there is a paper that might be helpful for your purpose:

Bird, A. F.. A method of distinguishing between living and dead
nematodes by enzymatically induced flourescence. Journal of Nematology
, 103-105. 1979

The author states that the technique is quick (results in 15 min).
Anyway, it makes the use of fluorescein diacetate (FDA) and
fluorescence necessary and I never tried it by myself.

Best, Daniel