The Path of Least Resistance

Although he's still a graduate student, Harvard's Jimmy Liao (pictured left) has accomplished something that many scientists at major research universities never achieve: a first-author article in Science . We tracked him down and asked him how he got where he is, and where he's headed. We learned that Liao, like the fish he studies, is remarkably well adapted for his chosen environment.

Next Wave: Tell us, in just a few sentences, what you've reported in your Science paper.

Jimmy Liao: We show that fish can use the energy of a turbulent-flow environment to help them swim forward. Specifically, rainbow trout use a unique swimming motion, which we termed the Kármán gait, that involves little muscle activity near the head when exposed to experimentally generated vortices. This small amount of muscle activity reflects corrective movements of the head and is drastically different from the whole-body pattern of muscle activity responsible for large, bending motions seen when trout swim in uniform flows. Although many theories have suggested that animals moving through a fluid environment (air or water) can benefit from vortices, there was no direct experimental evidence that demonstrates the mechanism and its effect on the physiology of the animal until now. Linking vortex interactions with decreased muscle activity supports a hydrodynamic explanation for fish distributions in schools and in current-swept habitats. So, for instance, by understanding how fish can use turbulence to save energy, we may be able to design fish passageways that provide "rest stops" for migrating fishes in the near future.

NW: How would you describe yourself? Are you a wildlife biologist? An evolutionary biologist? How did you end up working in this field? Is it a lifelong interest or something you stumbled into?

JL: I'm an evolutionary biologist interested in animal behavior. To understand behavior, I have approached questions from a biomechanical perspective as a graduate student, but I plan on investigating behavior at the neurological level as a postdoc. My interests are focused on fish behavior, ecology, and evolution.

I have always been obsessed with fishes, fishing, and fish behavior. I started fishing when I was 2, if you can believe it, in the duck pond at Prospect Park in New York City. From there my family moved to the suburbs, where I grew up catching fish, frogs, insects, turtles, and crayfish and turning our bathroom and living room into a zoo. So being a naturalist has definitely been a lifelong interest. It also helped that my dad was a passionate angler and that my parents managed a sushi restaurant, where I could poke and prod at a diversity of fishes from around the world. My parents were very tolerant; they endured live fish in the bathtub for days on end and preserved fish skins in the basement during my fish taxidermy phase in 4th grade.

NW: Your paper is a collaboration with scientists at Harvard and MIT. Can you describe the nature of the collaboration? Who did what?

JL: Having observed fishes in the field growing up, I was interested in how fish interact with the wakes of objects in the flow. I had talked this over with my adviser, George Lauder, and we were thinking about using rocks or spheres to generate predictable wakes that we could then visualize using a quantitative flow visualization technique. At about that same time, David Beal, who was doing his mechanical engineering degree at MIT under his adviser Michael Triantafyllou--it was on how foils interact with vortices to maximize thrust and propulsive efficiency--e-mailed me and asked how fish interact with vortices. I told him that I was planning on doing some experiments to find out and invited him over to take a look. From day one we got along very well personally and decided to tackle part of the problem together.

David is a really sharp engineer and immediately suggested that we use a hemicylinder to ensure that we generate consistent vortices. It was a really productive and enjoyable synergy between us; my fluid-dynamics questions would push David to think about things he hadn't considered before, and his biological questions did the same for me. There was quite a lot of data to analyze, and David wrote most of the programs that were essential for the analysis. Over the course of the project, both David and Michael taught George and me a lot about cylinder wakes and fluid dynamics in general and added to the sophistication of the project immeasurably. Once I learned the technique, I did the muscle-activity experiments largely on my own, but George, who is just a master experimentalist, generously spent several hours showing me the ins and outs of fish surgery.

NW: What was your role in the work?

JL: David and I designed, set up, and analyzed the flow visualization and kinematics work together. Intellectually we each had crucial breakthroughs throughout the project. We initially spent half the day watching the trout do nothing behind the cylinder, then at the end of the day I decided to increase the flow speed just to see what would happen. It was only then that the strength of the vortices shed from the cylinder was strong enough to elicit a response from the trout. Once we discovered this novel gait, we were off and running to figure out what the fish were actually doing and how. Another breakthrough came when, out of curiosity, I towed a dead trout behind the cylinder and saw that it produced thrust (i.e., went upstream). David then tracked down some references that proved such a mechanism was mathematically possible in sinusoidal flows such as a cylinder wake. I did the EMG experiments a few months later and wrote the article for Science shortly after.

NW: Describe your relationships with your Ph.D. adviser and your other collaborators. Do you speak with your adviser frequently? Is the relationship formal or informal? Is the lab you work in large or small?

JL: David Beal is a good friend of mine now, and we still keep in contact. Michael is a very busy man and I don't get to see him often, but we usually get to chat at meetings and he's been very helpful and encouraging when it comes to talks and job applications. My adviser is an amazing biologist and a true professional role model. He is incredibly energetic and enthusiastic about the work that goes on in the lab. I speak to him almost on a daily basis, and the interactions are fairly informal. Our lab is pretty small, about seven people including postdocs.

NW: By most measures, a paper in Science is a nice accomplishment for someone at your career stage. How did this come about? Were you seeking this result, or did you stumble on it? At what point did you begin to see this as a possible Science paper (as opposed to one for a lower profile journal)? At the risk of seeming immodest, to what do you attribute your success?

JL: I'll answer with a key to success, actually, because I believe in it and don't consider it immodest. I think the main qualities that got me here are curiosity and perseverance ... also, being conscientious of personal interactions, which includes respecting others in your lab and field.

Initially I didn't think that this topic was "big" enough for Science, but I was always excited by the practical applications of this work and the general biological implications. It wasn't until a professor outside my department suggested that I submit to Science that I even began to think about the possibility; a person at my stage usually doesn't have that kind of perspective yet. I sent it in with my fingers crossed just like everybody else.

NW: How long have you been at Harvard? Are you finishing your degree, or will you be there a while longer? What's the next step for you? Have you started to think long-term?

JL: This is my fifth year at Harvard. I'm defending my thesis this March. I have applied to a few postdoctoral fellowships for next year that will take me into the field of neurobiology and sensory systems. I've also started to apply for faculty jobs hoping for the experience of an interview. One can never start thinking about these things too early. So I'm on the academic track currently.

NW: What would you like to be doing in 10 years?

JL: Besides fly-fishing for bonefish on Christmas Island? I'd like to be answering questions about natural behaviors in the field by integrating various disciplines.

NW: Anything else you'd like to add?

JL: Just that I was really fortunate to work with good people during my graduate career. In terms of collaborations, I couldn't have asked for a better introduction. For me, I don't care how brilliant someone is; if I don't get along with them personally I won't want to spend a lot of time with them and collaborate. And lastly, persistence, humor, humility.

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