Entomophobes the world over can rest easy. Despite the fact that there are millions more of them than there are of us, insects are unlikely to ever dominate by size, as a Union faculty member and two students are studying.
Scott Kirkton, assistant professor of biology, recently returned from a four-day research project on oxygen delivery in grasshoppers at the Argonne National Laboratory in Argonne, Ill., a premier facility run by the Department of Energy and University of Chicago.
There, with the help of Lauren Hennessey ’11 and Leah Pepe ’11, he conducted research to better understand how oxygen delivery might change as the insects grow and age.
“There has been a long-established hypothesis that insect body size is limited by oxygen delivery,” Kirkton said.
In support of this hypothesis, 250 million years ago in the late Paleozoic, there is fossil evidence of hawk-sized dragonflies and other huge insects. But back then, it’s important to note, atmospheric oxygen levels were 35 percent as opposed to today’s 21 percent.
“It has been suggested that larger insects respire inefficiently and that’s why we don’t have gigantic sci-fi like insects running around. However, the hypothesis has not been well tested,” Kirkton said.
To better test whether larger insects have trouble breathing, Kirkton, Hennessey and Pepe carried out a critical piece of their work at the lab using an X-ray synchrotron, which allowed them to visualize the respiratory tracheal system of living insects.
Argonne’s Advanced Photon Source (APS), one of the most technologically complex machines in the world, provides the brightest x-ray beams in the Western Hemisphere for research in most scientific disciplines.
“Argonne is a pretty amazing place,” said Kirkton, who received a grant from the facility. “When allotted beam time, you are expected to work 24 hours a day to maximize your use of the facility.”
The technique of using X-rays to see inside a living insect has led to an explosion of work in the field, he added.
Kirkton, Hennessey and Pepe are also examining whether oxygen delivery to the jumping muscles in grasshoppers decreases with body size across instars or within instars, the week-long periods before grasshoppers molt and begin the next phase of development.
They are working in collaboration with Kendra Greenlee of North Dakota State University and one of her research students.
“Kendra is interested in caterpillar O2 delivery during development, while my lab works on O2 delivery to the muscle of jumping grasshoppers. Similar questions but with different organisms,” Kirkton said.
In 2008, he brought two students, Elizabeth Nyberg ’09 and Elizabeth Stanford ’09, to Argonne as part of a collaboration with Greenlee’s lab. From that work, they received the most recent grant for beam time to measure metabolic rate, ventilation rate and air sac compression of living insects.
In August, the group will collect data across instars and will measure the metabolism and air sac compression rate/depth in the smallest juveniles as well as adult grasshoppers.