>  Old ethanol preserved specimens are not a good source for DNA
>  sample because ethanol degregates the DNA after a while ( a few
>  years). Not very old samples could be used, but with caution.

They're certainly not as good as recently preserved specimens, and live is always best.  However, some details of ethanol preservation can help keep things better.  I have gotten good DNA out of samples that have been in ethanol for a few years.  It's important to make sure that the ethanol penetrates the tissue quickly.  Good solutions to this are to open the shell (if it closes with operculum, two valves, etc.), to get a slice of tissue if the animal is large, and to change the ethanol a few times soon after collecting (to compensate for the dilution due to water from the animal tissues).  Keeping the container well-sealed to keep ethanol in and water out is also important.

    Dr. David Campbell
    Old Seashells
    University of Alabama
    Biodiversity & Systematics
    Dept. Biological Sciences
    Box 870345
    Tuscaloosa, AL  35487-0345 USA
    [log in to unmask]

That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa

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