ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Nils Tack is an author on ‘ Going around the bend to understand the role of leg coalescence in metachronal swimming’, published in JEB. Nils is a Senior Research Associate in the lab of Prof. Monica Wilhelmus at Brown University, USA, investigating the energetics, biomechanics and hydrodynamics of swimming in marine organisms to uncover biomechanical principles of propulsion and energy efficiency, guiding the bioinspired design of advanced underwater vehicles.
Nils Tack
How did you become interested in biology?
My interest in biology began at the age of five when I received my first National Geographic underwater photography book by David Doubilet. The vivid imagery sparked a deep curiosity about underwater worlds, which I pursued by spending the next 12 summers snorkeling along a small rocky beach on France's North Atlantic coast. I eagerly observed and learned about as many marine species as I could. In my teens, I became scuba certified, allowing me to explore further, take underwater photos of my own and deepen my understanding of all the species I encountered. A pivotal moment came in 1999, when an oil spill from a tanker devastated the beach I knew so well. Witnessing the vulnerability of an ecosystem I had assumed was resilient made me realize the urgency of studying and protecting marine environments. Over the next decade, I returned each summer driven by curiosity, to observe the sequential changes in abundance, community composition and overall reconstruction of the local ecosystem. I was hooked! This long-term, first-hand experience transformed my early fascination for the spectacular recovery of a small, relatively unknown beach, into a commitment to research in marine biology.
Describe your scientific journey and your current research focus
My scientific journey began in France, where I was born and raised, and where I enrolled in a marine biology bachelor's program near Nice. The program's international structure allowed me to complete the first half in France before transferring to a partner institution abroad. I chose Roger Williams University in Rhode Island, where I was first introduced to particle image velocimetry (PIV) to study how small jellyfish interact with the surrounding water to feed on small plankton. This experience sparked a deeper interest in biomechanics, leading to an internship at the University of North Carolina Wilmington, USA, where I studied the histology and biomechanics of box jellyfish; fascinating animals that, despite lacking a central nervous system, use complex eyes to navigate their environment. Inspired by the interplay between biology and mechanics, I then pursued a PhD in Integrative Biology at the University of South Florida, USA, where I studied fish locomotion to understand how fish leverage interactions between their body and fins and water to optimize performance and energy efficiency. One of the driving motivations of my research was to inform the design of bioinspired underwater vehicles. This growing interest in bioinspired engineering brought me to Brown University, USA, for a postdoc in the Wilhelmus Lab. There, I combined my biological expertise with experimental fluid dynamics to study metachronal propulsion in shrimp, applying those insights to develop a shrimp-inspired underwater robot. Now a senior researcher in the lab, I lead a collaborative effort with the US Navy and other engineering teams at Brown to develop the first swarming, miniature, bioinspired underwater autonomous vehicles based on metachronal propulsion. Beyond the practical applications, we are using these robots as test platforms to investigate the fundamental principles of metachronal swimming, with the goal of developing a unifying theory that explains the widespread use of this propulsion mode across aquatic organisms.
How would you explain the main findings of your paper to a member of the public?
Many small underwater animals, such as shrimp, swim by moving a series of closely spaced legs in a wave-like pattern. Until now, it was thought that this motion mainly helped them push water backward to move forward. But our study shows that shrimp also use this movement to reduce drag, the resistance from water that normally slows them down. We discovered that shrimp bend their flexible legs and group them together during swimming, which helps them move more efficiently. To explore how this works, we studied live shrimp and built a robotic shrimp that could mimic the wave-like movements of shrimp legs. We found that bending can reduce the drag on each leg by up to 75% compared with stiff legs, and grouping them together boosts swimming performance by another 30%. Our research helps explain why so many aquatic animals use the same swimming mode as shrimp and can inspire the design of more efficient underwater robots.
Instantaneous velocity and vorticity field of a free-swimming marsh grass shrimp (Palaeomon vulgaris) obtained from bright-field particle image velocimetry. Shrimp leverage metachronal propulsion by allowing their flexible swimming legs to bend during the recovery stroke to mitigate fluid–structure interactions and facilitate the tight grouping of multiple legs to reduce drag and enhance overall swimming performance.
Instantaneous velocity and vorticity field of a free-swimming marsh grass shrimp (Palaeomon vulgaris) obtained from bright-field particle image velocimetry. Shrimp leverage metachronal propulsion by allowing their flexible swimming legs to bend during the recovery stroke to mitigate fluid–structure interactions and facilitate the tight grouping of multiple legs to reduce drag and enhance overall swimming performance.
What do you enjoy most about research, and why?
What I enjoy most about research is the opportunity to continuously learn and apply a broad range of skills while contributing to multiple disciplines. It may sound like an exaggeration, but researchers are very much the real James Bond and MacGyver – minus the fireworks and luxury cars. Interdisciplinary research demands critical technical and analytical abilities, whether in the lab or in the field, and we often work with our own specialized tools (gadgets?) and travel around the world for collaborations and fieldwork. What I truly value is that research becomes multidisciplinary naturally. Today, biologists increasingly rely on programming and engineering for data collection and analysis, while engineers often turn to nature for inspiration in solving complex design challenges. My own research journey has taken me from snorkeling in the Florida Keys to operating high-speed cameras and lasers in the lab, from programming and building underwater robots to participating in workshops in the French Alps. I especially enjoy integrating two seemingly distinct disciplines – biology and engineering – into a cohesive workflow. Studying how animals move reveals elegant and efficient strategies developed by nature over millions of years. These insights not only deepen our understanding of living systems but also inspire the development of innovative underwater technologies. Bridging these fields enables me to contribute to both scientific discovery and practical innovation, while fostering meaningful interdisciplinary collaboration. The added reward is sharing this work with both scientific and public audiences, and seeing how it resonates and inspires others.
What is the most important piece of equipment for your research, what does it do and what question did it help you address?
One of the most essential tools in my work is a high-resolution, high-speed camera. It allows me to capture and analyze rapid movements in small aquatic organisms that would otherwise be too fast to observe in detail. This type of camera is especially critical for studying fluid dynamics using techniques such as PIV, where we need to visualize how water moves around swimming shrimp or their robotic counterparts. By effectively slowing down time, I can achieve the temporal precision needed for accurate, high-resolution flow measurements.
Do you have a top tip for others just starting out at your career stage?
Be bold in your experimental and analytical approaches. While graduate training provides a strong foundation, there is always room to expand your skill set throughout your career. After completing my PhD in Integrative Biology, I joined an engineering team focused on developing bioinspired underwater vehicles, an area well outside my original expertise. I hadn't expected to be designing, programming and testing my own experimental robots, but embracing that challenge significantly expanded the scope of my research. Gaining these new technical skills has allowed me to lead projects that bridge biology and engineering, ultimately doubling the impact and versatility of my work.
What do you like to do in your free time?
In my free time, I enjoy hobbies that reflect my passion for both biology and engineering. I often spend time outdoors, crawling through bushes or mud to take macro-photographs of insects and other small creatures. Catching shrimp for a research project also counts as free-time activity. When I'm not in the field, I like to apply my skills in electronics and prototyping to work on personal robotics projects. These activities allow me to stay creatively engaged with nature and hands-on engineering.
Nils Tack's contact details: School of Engineering, Brown University, 345 Brook St, Providence, RI 02912, USA.
E-mail: [email protected]
