“Imagine if you were driving on a highway and you saw a billboard for McDonald's at the next exit. […] You get the Golden Arches and some attractive person holding a burger, or maybe you just get the picture of the fries. As your stomach growls at the sight of those crispy fries you think, ‘It’s a long way from San Bernardino to La Jolla…I should stop at the next exit and get a Mcdonald's, right?’” This dialogue from Cornell Professor Dr. Raguso paints a picture of very successful marketing. However, he poses the question of multisensory McDonald’s billboards. What if while you were driving on the California I-5, you not only saw those piping hot french fries crowning the bright red cup, but also smelled the sizzling oil? “That’s what a flower is,” a sweet smelling advertisement selling nectar to its pollinating customers.
Robert A. Raguso, researcher and full-time professor for the Department of Neurobiology and Behavior at Cornell University, has explored the intersection between the chemistry of scents and the behavioral biology of pollinators for roughly a decade, yielding several publications, inspired students, and the most surprising of results to this burgeoning field. He continues to teach students about the mechanistic, evolutionary, developmental, and functional aspects of animal behavior, as well as lead a research laboratory focusing on plant-pollinator communication, specifically by investigating the hawk moth species.
Smell seems to be the most underrated of the five senses. We, as humans, tend to focus on what we see when we drive, what we hear when a professor is lecturing, how our peanut butter and jelly sandwich tastes, or how a keyboard feels when we type words onto a page. However, how often do we stop to smell the roses? The most information we gather from smelling something is whether it smells good or bad. Maybe it makes us want to eat or maybe it motivates us to walk the other way. However, to insects, olfaction takes on a whole different meaning.
In the human brain, the olfactory bulb sits right below the limbic system (our reward system) and thus, is actually quite close to our amygdala, our emotional center, and hippocampus, our memory center. The fewer connections between the olfactory bulb and emotional and memory centers are one of the reasons certain smells can bring back emotional memories, such as peppermint and pine triggering recollections of Christmas. In contrast, insects have “a network of neurons in the antennae lobe” which forms “spherical structures called glomeruli” sitting in their antennae, the insect version of a nose. These sensory neurons connect the odors of the outside world to the olfactory center. Dr. Raguso makes the analogy that much like humans learn the smell of French fries when they are fresh, pollinators will learn to recognize particular scents of flowers that produce good nectar. “They learn particularly well when colors, shapes, and smells are combined,” Dr. Raguso says. As such, one of the broader questions Dr. Raguso asks is what ways do flowers communicate to pollinators?
Diving deeper into the specifics of his work, unlike many of his colleagues who focus on bees, Dr. Raguso specializes in hawk moths. Dr. Raguso explains that he looks at these in particular because “I grew up collecting insects, mainly butterflies and moths, so I simply knew more about them.” His other reason for picking this insect was its uniqueness among creatures of flight. With a whopping wingspan of 5 to 20 centimeters, the hawk moth is roughly the size of a hummingbird. They also have color vision and the ability to hover, both being traits not often seen in the animal world. As Dr. Raguso’s graduate thesis was on the genetics behind flower scent production, the leap from plant scent to how plant scents interact with pollinators was not a particularly large jump. Dr. Raguso noticed that hawk moths tended to visit heavily scented flowers. At the time, plant-pollinator relationships were studied almost exclusively with respect to flower color, so the new introduction of scent into the equation was essentially uncharted territory, and “[i]t was a way for me to spend years where everything I found was new.”
As his work involves both plant and animal observational work, Dr. Raguso has compartmentalized his laboratory to have plants growing in a greenhouse upstairs and colonies of insect pollinators that breed year-round in a separate space. Another part of his day-to-day work involves chemical work in order to understand the compositions of flower fragrances. Using gas chromatography and mass spectrometers, odors can be blended or separated and puffed over insects’ antennae to measure their olfactory responses, by combining a little bit of electrophysiology as well. When developing a laboratory that draws from multiple fields of study, several factors need to be considered. In order to mimic a natural setting for plants and insects to grow in, natural lighting and incubators maintain a certain circadian rhythm for the plants and insects. In the chemical analysis rooms, freezers housing certain compounds are constructed to be explosion-proof. When dealing with electrophysiology from the small voltage changes in antennae, the laboratory room must be grounded and supported by air tables to dampen the vibrations of general foot traffic.
During our interview, Dr. Raguso makes a point that his work is definitely not done alone, clarifying, “when people say ‘my lab’ as a scientist, they're almost always referring to their team.” Though some professors prefer to run a large corporate type of laboratory, Dr. Raguso prefers a close-knit team made up of just a few post-bac researchers, one or two graduate students, and maybe a couple of undergraduate students. In explaining his style, he says, “I don’t like larger labs because I don’t really get to know and work with the people in my lab. I don't want a huge lab where I’m kind of like a boss and where my job is mostly to write grants. So I tend to keep my labs small.” The lab compact sizing actually opens up many opportunities for summer and spring fieldwork, as Dr. Raguso will sometimes take his team to Colorado, Arizona, or even sometimes to the Southern Hemisphere regions such as South Africa or South America. Given that he lived in Chile, Argentina, and Ecuador, and thus is fluent in Spanish, he shares his experience with how the language has opened up a second world of possibilities. As certain concepts simply cannot be translated, he emphasizes that learning a second language and culture has made his conversations less superficial and more personable.
As Dr. Raguso continues his work, his research contributes to multiple broader fields of study including chemistry, behavioral biology, and plant science. However, to the average person, the distance by which a hawk moth can smell a lilac might sound like an interesting bit of information, but irrelevant to non-scientists. Dr. Raguso addresses this question by emphasizing that pollination, on a macro-level and from a human perspective, is involved with food production. Many of the main plant starches such as corn, potatoes, and gourds like pumpkins, squash, cucumbers, and melons require pollination. Moreover, he also reminds us that sometimes the most groundbreaking discoveries that have shaped modern technology and science have come from the most unlikely of places. For example, one of the most ubiquitously used bioluminescent markers used to track genes, GFP (Green Fluorescent Protein), was discovered in jellyfish by Osamu Shimomura, a young researcher who was simply curious about what made the crystal jelly glow in the dark. He cites this example in the conversation, making the point that research often just starts from curiosity, and sometimes the outcomes end up changing the world. Similarly, Dr. Raguso started with just a question about smells and bugs, but in following his calling, his work has expanded the field of animal-plant science beyond the minuscule collection of facts it was merely a decade ago.
References
Chen, KY, Kwong, HYH, & Szeto, DM. (2022). Green Fluorescent Protein: Its Development, Protein Engineering, and Applications in Protein Research. Journal of Young Investigators, 25(3), 19-32, available: 10.22186/25.3.1.1
Wolden, G. (2015) ‘Moths get wind of a partner from a kilometre away’, Norwegian University of Science and Technology. Available: https://partner.sciencenorway.no/forskningno-human-body-norway/moths-get-wind-of-partner-from-a-kilometre-away/1416404 [accessed 19 Oct 2022].
Andersson, M. N, Lofsterdt, C., Newcomb, R. D. (2015) ‘Insect olfaction and the evolution of receptor tuning’, Frontiers in Ecology and Evolition. May 20, available: https://www.frontiersin.org/articles/10.3389/fevo.2015.00053/full [accessed 19 Oct 2022].