The National Museum of Natural History safeguards millions of organisms ranging from mosses to mammoths. This detailed library of life is a vital resource for scientists, who have used the museum’s specimens for more than a century to identify, name and place new organisms in the taxonomic tree of life.
But access to historic museum collections is often limited to scientists with travel funds and the ability to securely send and receive specimens through the mail. As a result, researchers in areas with limited resources can struggle to name new organisms simply because they lack access to the global biological catologue held in natural history museums.
To democratize the museum’s collection, a team of Smithsonian scientists led by research zoologist and curator Karen Osborn are creating digital three-dimensional models of some of the museum’s most delicate specimens: marine segmented worms. Sometimes called scale worms, these specimens were originally described by noted biologist Marian Pettibone, who became the first female curator in the museum’s department of invertebrate zoology in 1963.
Thanks to cutting-edge micro-CT technology (a small-scale version of the technology doctors use to visualize internal injuries), digital models of Pettibone’s worm specimens are now easily accessible online as part of the Pettibone Legacy Project. This effort is making it possible for researchers around the world to re-examine Pettibone’s historic specimens in incredible detail right on their laptops.
To name a species
While all museum specimens are scientifically valuable, a certain few specimens are particularly important to researchers. Known as “type” specimens, these preserved organisms represent the scientific voucher used to describe and name entirely new species. The type specimen serves as the single specimen that represents that scientific name.
“Comparisons of new organisms to type material is critical to the discovery and documentation of new species,” said Brett Gonzalez, a postdoctoral fellow researching scale worms as part of the Pettibone Legacy Project. “Say you collect a worm in Bangladesh that looks very similar to one originally described from the Mediterrean Sea. To be sure they are different species, you have to compare the two in extreme detail, which simply cannot be done without access to type specimens.”
To make a large stockpile of name-bearing specimens accessible to researchers around the world, the Pettibone Legacy Project is digitizing 170 marine segmented worms Pettibone described during her nearly four decades at the museum.
“With the help of a micro-CT scanner, we can create a three-dimensional digital model,” Osborn said. “These models are so detailed that they can serve as a virtual type specimen, allowing outside researchers to examine them without needing to come to the museum.”
The mighty power of micro-CT
To craft these virtual worms, specimens are first stained with heavy metal molecules (like tungsten) to refract x-rays, then mounted in the micro-CT machine. As the specimen rotates around, the machine takes hundreds to thousands of x-ray images, which are spliced together to create 3D models. Advanced software can then cut these virtual models into paper-thin slices that allow researchers to explore the internal and external anatomy of the organism in detail.
After the scan, the worm specimen goes right back into its collection jar. “For centuries, scientists have relied primarily on careful external inspection of type specimens – anything more invasive risks permanently damaging these invaluable organisms,” said Victor Conde-Vela, a postdoctoral researcher working with the Pettibone Legacy Project. “With a micro-CT scan, we can explore the inner workings of the worm without dissecting or destroying the specimen.”
With the micro-CT scanner, these type specimens are now even more scientifically valuable. In 2021 a team of scientists that included Gonzalez, Osborn and their collaborators at the University of Copenhagen demonstrated how micro-CT scanning can reveal adaptations to different environments.
The team used micro-CT scans of several species to study the evolution of swimming muscles in scale worms. While most scale worms crawl on the seafloor, some spend their entire lives swimming or drifting in ocean currents.
Using micro-CT scans, the team analyzed the differences in the muscles of the crawling or swimming appendages found in several different scale worms. While the worms all have the same muscle groups, evolution has tweaked each species’ musculature to help certain worms drift, swim or crawl.While understanding how scale worms wiggle may seem niche, these insights provide crucial context to the evolution of movement in other groups of animals. In the future, these squirming scale worms may even help researchers calibrate movement in robots
The future of museums
Over the past 12 months, the team has sent over 100 type specimens from Pettibone’s collection to the University of Texas Austin for micro-CT scanning. Each scan will be turned into a video “fly-through”, where the compiled 3D model can be viewed layer by layer from any angle, as if the viewer were a camera moving through the worm. These videos will be available to download from the museum’s online catalog for anyone with a computer and internet connection.
Through the work of the Pettibone Legacy Project, the trove of biological data sealed within the museum’s specimen jars will only be a few clicks away.
“I love the fact that soon, a researcher in Namibia can compare the species they find to types held in our collections in a matter of minutes,” Osborn said. “All they need is a laptop or cell phone.”
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