After three hours compiling close to a thousand super-high-resolution images, Chip Austin has produced a 3D x-ray image of a bug that might make your skin crawl. Austin, a graduate student in entomology, studies the structures of insects, from the squishy organs to the hairy antennae to the piercing claws.
Austin has captured the images with the help of an Xradia MicroCT, a microscope in Beckman’s Microscopy Suite, which is capable of extremely high-resolution 3D x-ray images.
In order to examine the evolutionary histories and family tree of a certain superorder of insects, called Paraneoptera, Austin scans individual insects with the microCT to see minute details. Paraneoptera include bark lice; parasitic lice; hemipterans (cicadas, aphids, leafhoppers, and others); and thrips, which are tiny plant-dwelling insects.
“To document the morphology, or the specific structural features of the organisms, I look at the physical characteristics. There’s been some morphological research done on this group, but there are a lot of gaps, and you need fill in these gaps to make a phylogeny of these insects, which is their evolutionary family tree,” said Austin, who is advised by Chris Dietrich, a systemic entomologist working with the Illinois Natural History Survey (INHS).
MicroCT scans provide a great source of information. With microCT, you basically preserve the location of all the organs in 3D space, without tearing it up, like you do with dissection. It’s all there and intact.- Chip Austin
With this information, Austin can start to make connections in the evolutionary histories of Paraneoptera. Austin is doing this research as part of a larger project headed by Dietrich and Kevin Johnson (also at INHS), funded by the National Science Foundation’s Assembling the Tree of Life (AToL) initiative. The goal of AToL is to create a working phylogeny for all life on Earth utilizing modern genetic and morphological analysis techniques.
“Our project is to make the tree of life for Paraneoptera,” said Austin. “Ultimate results of the project will be not only a more accurate phylogeny, but also a wealth of information on which to base future research on the group’s evolution, ecology, developmental biology, and more.”
While some analysis can be done with more common microscopes and through dissection, microCT offers an unparalleled look inside the insects.
“MicroCT scans provide a great source of information. With microCT, you basically preserve the location of all the organs in 3D space, without tearing it up, like you do with dissection. It’s all there and intact,” said Austin. “It’s always exciting with the microCT—no matter how many times you look at it, you’re always going to find something new and surprising.”
To image an insect, Austin places a dried sample into the bore of the microscope. After some manual maneuvering and focusing, the microscope rotates the insect 360 degrees and takes up to 900 pictures of small sections of the insect.
The images are combined in a software program that renders an image in 3D, with the capability to highlight certain areas of the scan, such as particular organs.
“My main goal with using microCT is to document a couple of larger groups of insects, like litter bugs and jumping plant lice, that have very little morphological documentation," Austin said. "They’re really small and very cryptic insects.”
Austin plans to document 300 different details, also known as characters, of the insects in the superorder Paraneoptera. Filling gaps in data is important for making the tree as accurate as possible. Otherwise, there may be unifying traits or diversifying changes that are left unaccounted for.
“I want to maximize data coverage,” Austin said. “Looking only at an insect’s wings or legs can give you a starting idea of how closely related it is to other groups of insects, but in order to get the whole story, you need a lot more evidence.”
The insect samples are from the Natural History Survey at the University of Illinois, with most of the insects coming from either Illinois or Chile, the latter collected by Dietrich.
The Beckman Institute Microscopy Suite has the only microCT scanner on campus, which is available to students and faculty across campus.