Door 21 – Persistent considerations for molecular analyses of museum specimens

Many factors come into play when making decisions about using museum specimens, especially for molecular applications. As a museum scientist that utilizes molecular methodologies, I am constantly conducting experiments in my mind to try to run through how each step and/or technique will (or won’t) get me to the kind of information (data) I need. Doing these mind exercises is foremost, important because molecular methods are destructive. Where we gain solutions (e.g., DNA extracts) of extracted biomolecules, we also accept that there is no longer the possibility of returning the sample tissues (e.g., teeth, bone, muscle etc.) that were taken.

What has recently made molecular analyses so exciting is that many have progressed to a point where smaller and smaller sample amounts are required, that then deliver large amounts of data, at increasingly lower costs. This outlook of high reward for molecular analyses has led to a massive increase in destructive sampling requests within museums. However, as it is often the case with high reward endeavors, there is also generally high risk in using museum collections for molecular analyses, such as ancient DNA. Coupled to the concern surrounding the destructive nature of molecular analyses, is also the concern that the methods may not yield applicable data. This is because as time goes on molecules degenerate, loosing properties and information that current methods may rely upon. Molecular degradation can also be exacerbated by various preservation techniques, usually in the form of chemicals, that are applied to museum collections (e.g., ethanol, formalin, arsenic, etc.). The good news is that technology and protocol specifications have allowed us to retrieve relevant data from increasingly older and degraded samples, thus, increasing the molecular potential of many museum collections and allowing for the scientific process to proceed.

Conducting experiments hypothetically is particularly important for gauging the molecular potential of the available collections relative to the scientific question being asked. Developing an approach for answering molecular analyses on museum collections depends on many things, including: the species being investigated, if the species is available and accessible in collections, which parts of an individual are available (i.e., which tissues), whether specialized equipment and protocols are available, affordable, and easily learned, if preservatives were used, which tissue will provide the most molecules, and many, many others. The ultimate determinations to make are understanding how much/little sample you can take to not sacrifice too much of irreplaceable specimens, knowing how and why specific procedures will be used, while also ensuring you get as much data as possible.

This is or can be a tricky, but achievable, balancing act. But, for as much literature is available about species, individuals, museum collections, the molecules themselves, the impact of time, and for understanding how methodologies work, there is even more, invisible information contained within museum collections. With the caveat of many considerations (and permissions), it is these invisible stories that molecular analyses can illuminate.

For further insight, read: Burrell, Andrew S., Todd R. Disotell, and Christina M. Bergey. “The use of museum specimens with high-throughput DNA sequencers.” Journal of human evolution 79 (2015): 35-44.

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