Natural history collections in museums and academic institutions contain a wealth of specimens that could be used to construct a DNA reference library. The specimens are invaluable; collectively, they constitute a partial documentation of biodiversity and they serve as the tools for evolutionary and comparative physiology and for many other disciplines. More important, many of those specimens are irreplaceable. Many natural history collection specimens are flxed and sometimes stored in formalin, which is inexpensive, widely available and effective, although it is an environmental toxin. A saturated solution of formaldehyde (CH2O) in water, formalin is about 37 percent formaldehyde by weight, and a standard flxation solution is 10 percent formalin in water, buffered to about pH 7. Formalin prevents degradation of specimens by microorganisms, and because it stabilizes and maintains the flne structure of soft tissue, it is still a widely used flxative.
Aside from its toxic properties, formalin has another shortcoming—its use alters the DNA in samples. When they are exposed directly to formalin, mammalian cells undergo genetic and chromosomal alterations. Pathologists and other biomedical researchers who use archival tissue samples taken during epidemics, for example, or from victims of rare diseases have had some success in extracting DNA from formalin-flxed samples, but those samples have been embedded in paraffln rather than suspended in aqueous formalin or ethanol. Few of the many attempts to obtain and sequence DNA from formalin-flxed specimens stored in aqueous formalin or ethanol have been successful (Shedlock et al., 1997; Schander and Halanych, 2003). All of the protocols are slow, difflcult, and often expensive, and few produce DNA fragments longer than 500 base pairs. Development of an effective protocol for recovering DNA sequence information from specimens flxed in formalin and stored in formalin or alcohol will give access to sequence information for thousands of species that are extinct, rare, or difflcult to re-collect.
At the request of the Consortium for the Barcode of Life, the Museum of Comparative Zoology of Harvard University, the National Evolutionary Synthesis Center, New England Biolabs, Inc., Sigma-Aldrich Company, the U.S. Department of Agriculture’s Agriculture Research Service, and the U.S. Environmental Protection Agency’s Environmental Monitoring and