Analyzing Darwin’s specimens without opening 200-year-old jars

Scientists have successfully analyzed Charles Darwin’s original specimens from his HMS Beagle voyage (1831 to 1836) to the Galapagos Islands.

Remarkably, the specimens have been analyzed without opening their 200-year-old preservation jars.

Examining 46 historic specimens

The study examined 46 historic specimens at the Natural History Museum, London, including mammals, reptiles, fish, jellyfish, and shrimps collected by Darwin and other naturalists. The work is published in the journal ACS Omega.

It was found that traditional preservation methods differed by species and era.

Mammals and reptiles were typically fixed in formalin and stored in ethanol, while invertebrates might be kept in formalin, buffered solutions, or mixtures containing additives like glycerol.

80% of samples correctly identified

The technique correctly identified fluids in approximately 80% of cases tested, with partial identification in another 15%.

It also determined the types of glass or plastic containers used, providing insights into how storage methods have evolved over time.

The research was conducted by a collaboration between the Science and Technology Facilities Council (STFC), the Natural History Museum and Agilent Technologies.

Portable laser techniques

Researchers used a portable laser spectroscopy method called Spatially Offset Raman Spectroscopy (SORS) to peer through glass and identify the chemical composition of preservation fluids.

SORS performs chemical analysis by shining a laser light into a container and inspecting the changes in wavelength that occur when the light is reflected.

These changes indicate the presence of different chemical components within it.

SORS, originally developed at STFC’s Central Laser Facility, is the same technique which is used in airport scanners all over the world through Agilent Technologies.

Dr. Sara Mosca, STFC Central Laser Facility said, “Until now, understanding what preservation fluid is in each jar meant opening them, which risks evaporation, contamination, and exposing specimens to environmental damage. This technique allows us to monitor and care for these invaluable specimens without compromising their integrity.”

Impact for museums worldwide

There are over 100 million fluid-preserved specimens housed in museums worldwide.

For collection curators, knowing the exact composition of preservation fluids is essential for monitoring specimen condition.

The ability to analyze preservation fluids non-invasively offers conservators and curators a new tool for monitoring collection health and intervening before problems arise.

Transforming the study of natural history

Wren Montgomery, research technician at the Natural History Museum, says, “As part of NHM Unlocked, here at the Museum we can analyze jars containing specimens without opening and disturbing their integrity. This work is the next step in demonstrating the Museum’s commitment to transforming the study of natural history.

“Analyzing the storage conditions of precious specimens, and understanding the fluid in which they are kept, could have huge implications for how we care for collections and preserve them for future research for years to come.”