As several people have mentioned, the easiest way to preserve specimens for
DNA studies is with ethanol.  If you do not have access to reagent-grade
ethanol, the strongest stuff from your local liquor store is probably
adequate for short-term storage.  The DNA is preserved in the best
condition if the animal is kept alive, but this may not be easy.  Keeping
the sample cold is also a good idea, though not necessary
(ethanol-preserved specimens did fine for two weeks in the Philippines
without refrigeration).
 
Especially if you are starting with less than 100% ethanol, it may be
necessary to change the ethanol as fluids from the animal dilute the
original solution.  For clams or tall-spired snails, it may be necessary to
open or break the shell to ensure that the ethanol reaches the animal
rapidly.  Large-bodied animals may require cutting up or injection of the
preservative to ensure that the inside is penetrated.
 
Mantle tissue is often hard to work with for DNA studies, since the
mucoproteins can interfere with some of the reactions.  The digestive tract
is also to be avoided, since it may contain foreign DNA.  Apart from that,
if the animal is large, a piece of tissue will contain plenty of material
for DNA studies.  Thus, a compromise could be to cut out an anatomically
uninteresting piece and put it in ethanol and then put the rest into
formalin.
 
One caution when using preservatives is that many of them can dissolve
plastics and inks.  I have had problems with cheap zip-closure bags leaking
when I put ethanol in them, though water did not leak out.  Likewise,
laundry markers are not permanent if ethanol is applied.
 
Also keep in mind the health risks posed by some preservatives.  Work in a
well-ventillated area, away from anything that might ignite fumes.
 
 
 
David Campbell
 
"Old Seashells"
 
Department of Geology
CB 3315 Mitchell Hall
University of North Carolina at Chapel Hill
Chapel Hill NC 27599-3315
USA
 
919-962-0685
FAX 919-966-4519
 
"He had discovered an unknown bivalve, forming a new genus"-E. A. Poe, The
Gold Bug