Clemson scientists unraveling astonishing complexities of the butterfly proboscis
CLEMSON, South Carolina — A pair of Clemson University scientists has spent the past decade exploring the unique intricacies of a naturally engineered feeding tube that butterflies and other insects have been refining for 200 million years.
Although the insects have a rather large head start, the scientists are doing their best to catch up by successively unveiling an array of discoveries that are shaping the way biologists, materials scientists and engineers understand the mechanisms of one of nature’s most multifarious body parts. This ever-increasing fount of knowledge is expected to eventually lead to manufactured devices that could revolutionize medical procedures and other yet-to-be-conceived applications.
Since 2007, entomologist Peter Adler and engineer Kostya Kornev have blended their diverse skill sets to study the proboscises of butterflies, moths and other varieties of fluid-feeding insects that use these flexible mouthparts to acquire food from sources as diverse as nectar, soil, dung and carrion.
Biologists once believed that the proboscis (pronounced pro-BOSS-ciss) was a simple tube that drew up liquids like a straw. But Adler, Kornev and their students and associates, including Clemson research specialist Charles Beard, have worked incessantly to reveal that the proboscis is an astonishingly complex marvel of nature, as proficient as it is diverse. Recent advancements in their research have further quickened the pace of their explorations.
“We have been able to show that the proboscis is actually many times more sophisticated than a straw,” said Adler, a professor of entomology at Clemson University. “Instead, it is a self-cleaning microfluidic system made up of two C-shaped fibers that unite to form a food canal that is laden with pores, sensors, internal muscles and other tissues. And depending on the species, it is often covered with shingles, spines or bumps. The proboscis is able to acquire sticky fluids that potentially contain bacteria, yet remain squeaky clean and uninfected in the process. How is this accomplished? The surface of this tiny tube contains a mosaic of hydrophilic (water-loving) and hydrophobic (water-repellant) properties that enable the insects to drink and self-clean almost simultaneously. This paradoxical juggling act is essential to their survival.”
The unconventional marriage of Adler’s expertise in entomology and biology and Kornev’s mastery of materials science and engineering has benefitted both parties and significantly enhanced the research. Adler has spent his career studying how living organisms adapt, behave and evolve in ways that engineers might not even consider. In complementary fashion, Kornev has the knowledge of materials science and physical principles and the know-how to operate highly sophisticated equipment not often employed by biologists.
“Every time we open a new door, we find five more doors behind it,” said Kornev, a professor of materials science and engineering at Clemson. “But our projects are driven by scientific curiosity and passion about both the engineering and biology. The proboscis is unique in the sense that it is fibrous and, at the same time, a sensor-driven delivery system for fluid intake. So looking at how these fibers are assembled is a big challenge that can help engineers design a variety of fluidic devices — medical and otherwise — that are tiny, flexible and durable. It is exciting to imagine what the future might hold, but for now we are doing our best just to learn as much as we can about the proboscis.”
The proboscis is attached to the insect’s head, where a pump helps power the slew of sponge-like mechanisms that draw up fluids. Many proboscises are less than an inch long, but some reach 14 inches, dwarfing the length of the insect’s entire body. However, all insect proboscises are miniature in terms of diameter — about 15 times thicker than a human hair — which makes them difficult to study without the use of sophisticated equipment, such as electron microscopes and micro-CT scanners.
But Adler and Kornev routinely use this high-tech equipment — both at Clemson and at a pair of national laboratories — to examine proboscises in excruciatingly intimate detail. Because of this, their understanding of the proboscis places them at the top of the scientific community.
“We want to get to the heart and soul of how proboscises work, and we’ve recently come to understand a lot of the processes that occur at the micro- and nano-levels,” said Adler, who first became fascinated with the workings and diversity of proboscises when he was a graduate student at Penn State in the 1970s. “I would characterize our advances as quite significant because they provide new models for fluid uptake not just in butterflies and moths but in any insect that has sucking mouth parts, including insect pests that damage crops. There are more than one million known species of insects in the world and potentially as many as 10 million species overall, most of which have yet to be discovered. About 50 percent of all these species suck fluids, so the diversity is almost overwhelming.”
“But this is how science works,” added Kornev, who supervises materials science and engineering Ph.D students Luke Sande and Chengqi Zhang. “Life is too short to cover everything. So what we do instead is take on the most challenging paradoxes that drive the development of the bigger picture.”
During their 10-year collaboration, the entomologist and the engineer have been assisted by several dozen scientists, research assistants, postdocs, graduate students and college and high school students at Adler’s lab at the Cherry Farm Insectaries and at Kornev’s lab at Sirrine Hall. Adler described them as “ambassadors not just for Clemson University, but for science and nature. Once they’ve spent time at Clemson, whether it’s for a single summer or several years, all these people then go out in the world and influence others in very positive and beneficial ways.”
One such ambassador is Matthew S. Lehnert, who joined Adler and Kornev’s team in 2010 as a postdoctoral scholar after receiving his Ph.D at the University of Florida. Lehnert is now a research scientist and assistant professor at Kent State University at Stark in North Canton, Ohio, and he plans to devote most of his career to an ongoing study of the proboscis. Lehnert is a co-investigator — along with Adler and Kornev — of a three-year, $626,800 National Science Foundation grant that has just begun its final year. This grant is one of several that has fueled the projects since 2007. More grants are certain to come that will continue to give wings to the research.
“I think I was a bit naïve when I started working at Clemson, thinking that the proboscis is a pretty simple thing. Now I know that it is a very complex device loaded with microstructures that all play different roles in the feeding process,” said Lehnert, adding that his students at Kent State seem as passionate about the research as he is.
“Because of this cool collaboration between biologists and engineers, we know so much more than we did just two years ago. It’s been exciting to constantly find new and unexpected things. It really is incredible what these proboscises are capable of doing, and the more we can learn about them, the more we will benefit down the road. The possibilities seem limitless.”
This material is based upon work supported by the National Science Foundation under grant number IOS 1354956. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.