Many years ago, the only way entomologists could reproduce an ant in three dimensions was by using sculpting clay and their best artistic talent for rendering accurate proportions. Computer programs and improvements in photo technology helped increase the accuracy of 3D models, but recreating an entire creature, no matter how small, still involved a lot of work.
But now, researchers are using particle accelerator equipment to scan whole trays of ant specimens at a time. The process takes a minute or two per scan and faithfully reproduces a 3D model of the inside and outside of ants.
“It’s sort of like a medical CT scan, but the resolution is really high,” said Evan Economo, an entomology professor at the University of Maryland.
In a study published recently in Nature Methods, Economo and his colleagues describe their new technique, which uses high-throughput synchrotron X-ray microtomography—a technology a little bit like the CT scanners used by doctors looking for things like cancer—and a robotic sample change system that quickly switches out samples of individual ants.
The synchrotron machine at the Karlsruhe Institute of Technology in Germany is often booked up. As a result, the team only had a week’s opening to work with, so they made sure to prepare.
Tracking down ant specimens
Economo and a team, including Julian Katzke, an entomologist at the Smithsonian National Museum of Natural History, spent months borrowing specimens from entomology collections. As a result, the new paper describing the technique has more than 50 authors—university professors, museum curators, institutional scientists and private collectors mailed the team samples from all around the world.
Once they had their specimens, the researchers had to prepare them for scanning. They filled glass bottles about the size of an eye drop product with alcohol and put an individual ant specimen in each. They set these into trays of 50, then would replace the tray after all the specimens were scanned.
By using this system they’ve dubbed “Antscan,” they have now created accurate 3D models of more than 2,200 individual ants from more than 800 species. The 3D models are available to researchers on a growing database they are adding to as they gather more samples from around the world to scan.
While previous technology using CT scans could produce these types of images, it often took more than 10 hours. The specimens that the team has now scanned make up more than all previous efforts to 3D-scan ants combined.
The team ended up getting scans from ant genera from most of the common groups. “There was a lot of rare stuff out there that we didn’t get,” Economo said.
Economo and Katzke are excited about the kind of research that this baseline work will facilitate. Researchers around the world can now access detailed 3D models of these species online, making it much easier to study anything from brain size and structure to how specimens might change over time, adapting to factors like climate change.
They also got multiple specimens scanned of species of concern, such as invasive species like red imported fire ants (Solenopsis invicta), that are causing problems around the world. Physiology studies may help researchers understand how invasive ants are so successful at colonizing new areas or how aspects of their physiology might help wildlife managers fight against them.
The future of Antscan
Economo and Katzke themselves already published work using these scans to measure and compare the thickness of exoskeletons in different ant species.
Researchers, or even teachers, can even take these scans to a 3D printer, making large-scale physical models, according to the team.
For now, their work on Antscan isn’t finished. They are still processing data from their second turn at the machine, which includes many Australian specimens. There are more than 15,000 ant species in the world, and the team hopes to get as many of those scanned as possible. Economo also said it would be nice to have different castes of each species scanned—queens, workers and soldiers, for example.
The researchers said that the technique isn’t just limited to ants. While the machine has size limitations, anything that fits in the bottles could be scanned—modern or not. The technique has already been used for scanning ancient specimens trapped in amber.
Article by Joshua Rapp Learn
