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CO2 pads

Dr. Alan Christensen christen at CALVIN.JCI.TJU.EDU
Mon May 9 13:58:50 EST 1994

There have been a couple of requests for information on where to buy
CO2 pads for Drosophila.  We have not found a supplier, but have made our
own as follows.  They are simply boxes of plexiglas, made with 1/4"
thick plexiglas, about 4" X 6" X 1" (sorry about the non-metric 
measurements, but we had a machinist make them, and he is non-metric).
On one side a threaded hole is drilled, and a fitting that accepts the
tubing that comes from the CO2 tank is screwed in.  On the top is a grid
of 1/16" holes drilled at 3/8" center-to-center.  We then cut a piece of
Nitex nylon mesh with 100micron holes to fit the top, and attach it with 
double-sticky tape around the edge, and little bits of double-sticky tape
scattered over the surface (but between the holes).  This works admirably
for keeping flies anesthetized for long periods of time.  We usually set
the regulator to 5psi, and adjust the flow rate with valves as sold in 
aquarium supply stores.  

Porous polyethylene or plexiglas is also available from plastic suppliers
and can be used for the tops, but the advantage of the Nitex top is that 
it is smoother, cleanable, and replaceable.  It could be changed frequently
in case of mites, for instance, or if flies get smashed into it.  More and 
smaller holes in the top would probably be better, but this grid works fine.
We have another one with 1/8" holes at 1/2" intervals that works OK.

In practice static electricity can be a problem.  Static charges seem to
get on the flies, the nitex mesh on the pads, and the plastic vials. 
Occasionally, the vials will repel the flies, and they go all over.
A simple solution is a device sold in record stores as a destatic device
for vinyl records.  It is an alpha emitter, and works quite nicely.
I don't know if it is mutagenic, but that seems unlikely. 

Alan C. Christensen, Ph.D.                              215-955-5190
Dept. of Biochemistry & Molecular Biology           FAX 215-955-5393
Thomas Jefferson University              christen at calvin.jci.tju.edu
233 S. 10th Street                    
Philadelphia, PA 19107-5541                "Curiouser and curiouser"

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