Scientists Uncover Secrets of Darwin's Preserved Specimens Using Lasers
For over two centuries, Charles Darwin's precious specimens from his HMS Beagle voyage to the Galapagos have remained sealed in jars at the Natural History Museum in London. Now, a groundbreaking technique using lasers has provided an unprecedented glimpse into their contents.
Darwin's groundbreaking theory of natural selection and evolution, largely based on his observations during the HMS Beagle voyage, has shaped our understanding of the natural world. His preserved specimens, which include mammals, reptiles, fish, and shrimps, offer a window into the past, allowing scientists to study the changes that have occurred over time.
However, until recently, analyzing the preservation fluids in these jars without opening them was impossible. The risk of evaporation, contamination, and environmental damage made it necessary to crack open the jars, compromising their integrity.
Enter spatially offset Raman spectroscopy (SORS), a portable laser technique that measures the 'excitement' in a material's molecular structure. By taking multiple Raman measurements at different offsets, SORS can reveal the chemical signatures of both the surface and subsurface of the preservation fluids.
In a study published in ACS Omega, researchers applied SORS to Darwin's jars, achieving remarkable results. They accurately identified the preservation fluids in nearly 80% of the jars, with partial accuracy in another 15%. Only 6.5% of the samples remained unidentified, a testament to the power of this non-invasive technique.
The study revealed fascinating insights into the preservation methods used by Darwin. Mammals and reptiles were often 'fixed' with formalin and then suspended in ethanol. In contrast, invertebrates, such as jellyfish and shrimp, were stored in formaldehyde or buffered formaldehyde, sometimes with glycerol or phenoxetol added to maintain tissue integrity.
This breakthrough has significant implications for the care and preservation of not just Darwin's collection but also the over 100 million fluid-preserved specimens housed in museums worldwide. By using SORS, scientists can monitor and maintain these invaluable specimens without compromising their integrity.
The research team, including Wren Montgomery and Sara Mosca, highlights the importance of understanding preservation fluid composition for the long-term care and research value of these collections. Their work paves the way for more effective conservation methods and ensures that these historical treasures remain accessible for future generations.
