Calls of the Wild
In a Regents Hall neurobiology lab, Kari Jirik ’20 carefully tethers a fly to an insect-sized treadmill. She closes the door to the soundproof room that houses the treadmill system, then flips on the speakers that pipe male cricket songs into the small space. As the fly locates the direction of the singing male cricket and attempts to walk toward it, Jirik tracks the fly’s movements.
In this experiment, which is part of the Collaborative Undergraduate Research and Inquiry (CURI) program at St. Olaf, Jirik and a team of student researchers are testing the directional hearing capabilities of the fly. Along the way, they’re gaining invaluable hands-on experience in the scientific process.
“Sometimes, it’s necessary to have plan B, C, and D when working with these flies,” says Jirik. “Research is hard, and it takes time and effort to solve the problems that arise. We have all learned to be more flexible and adaptable.”
That persistence and flexibility come in handy when studying a creature as tiny as Ormia ochracea, an acoustic parasitoid fly, whose powerful hearing ability is the subject of a summer research project conducted by Assistant Professor of Biology Norman Lee in collaboration with his team of CURI students.
To study the auditory system of the O. ochracea, Lee and the student researchers are taking advantage of the predator-prey relationship between the flies and crickets. One might expect the crickets to be the predator and flies to be the prey. But with O. ochracea, says Lee, the relationship is the exact opposite.
“You have this interesting problem where male crickets advertise for female crickets by producing these attractive calling songs. But at the same time, male crickets will also attract these flies that will be deadly to them,” Lee explains. “So these male crickets are singing in the dark trying to attract female crickets, and at the same time, eavesdropping female flies need to find a host for their larvae to develop in, and they are using their sense of directional hearing to find these crickets.”
Lee explains that to survive, the flies have evolved these “fantastically cool ears” that allow them to eavesdrop on the communication signals of field crickets and to determine the direction from which the sound is traveling. In the Neural Systems and Behavior Lab, also called the Lee Lab, Lee and CURI students have homed in on the directional hearing that the O. ochracea has developed.
“The most interesting piece of information that I extracted this summer is that no ‘simple’ organism or system exists,” says Luis J. Almanza ’20, Lee Lab researcher and CURI participant. “Each organism possesses a new set of challenges that, in most cases, very few individuals in the world have studied. For our lab and myself, we are the pioneers, the trailblazers making way into a lane of work that quite literally no one else in the world may be doing.”
While the research is helping the research team understand how nervous systems function to mediate adaptive behavioral decisions in animals, it also has scientific, real-world implications for humans.
“My biggest takeaway with the CURI program was learning that I really enjoy the scientific process of in-depth research. I’m now thinking of pursuing a degree in audiology.” — Kari Jirik ’20
The ability to recognize sound patterns is common among many animals, including human beings, who rely on the patterning of sound to perceive speech and the direction from which a sound originates to determine the speaker location. “Humans find sound direction by [unconsciously] measuring the time difference between when a sound arrives at each ear,” says Lee. “Our ears are separated by enough distance that it gives our auditory system the ability to extract the location of a sound based on that time difference. We can also measure an intensity difference, so sound from one side will appear louder to my near ear than my far ear.”
Though this auditory process works well for humans and other large animals, the ears of the tiny flies in the Lee Lab are so close together that it should be physically impossible for them to determine sound direction because these time and intensity differences are so small. Yet the flies have been able to find host crickets based on their hearing ability, an ability they have gained through the process of evolution.
Lee believes that his research into O. ochracea hearing can be harnessed to help improve human hearing by providing engineers with insights into how the natural world has solved common hearing challenges such as perceiving salient sound sources in the presence of natural noise. Engineers have relied on biomimicry to design miniature microphones based on O. ochracea ears. “These insights may provide engineers with ideas to improve how natural stimuli are converted to electrical signals and how these signals are processed by speech recognition systems to improve hearing aid technology in a directionally sensitive way”.
While the findings that come from this research are important, Lee sees additional value in students’ experience of doing real research in an undergraduate setting. “I hope that students learn a set of transferable skills that will bring them success in their future endeavors,” he says. These skills include critical thinking, effective communication, and problem solving using a scientific approach. The students are also honing their technical skills, which include computer programming, data analysis, and graphical representation of their research.
In August, the CURI student researchers attended the 56th Annual Conference of the Animal Behavior Society in Chicago, where they presented the subject of their research, “Does spatial separation of cricket songs facilitate song recognition in Ormia ochracea.”
“It was amazing to be able to share the information we had learned over the summer with the greater scientific community,” says Jirik, who has discovered a newfound interest in scientific research. “From an academic standpoint, my biggest takeaway this summer with the CURI program was learning that I really enjoy the scientific process of in-depth research. It also led me to realize that I am really interested in hearing, and I’m now thinking of pursuing a degree in audiology.”
For Luis Almanza, the most rewarding part of his experience in the Lee Lab has been learning to fail in a scientific environment. “It is easy to become disappointed when an experiment you planned for months goes not as planned and yields little to no results,” he says. “However, it is in those times when you re-evaluate your situation and determine what needs to change rather than moving on.”
A new study by Dr. Norman Lee, in collaboration with St. Olaf College students Alexander Kirtley ’19, Isaiah Pressman ’19, and Karina (Kari) Jirik ’20, and other collaborators at the University of Toronto, show a novel approach that can be used to study song recognition in Ormia ochracea. Their research has been published in Frontiers in Ecology and Evolution, as part of the research topic How Enemies Shape Communication Systems: Sensory Strategies of Prey to Avoid Eavesdropping Predators and Parasites.