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. Luis Kuchenmüller is an author on ‘ Hyperoxia disproportionally benefits the aerobic performance of large fish at elevated temperature’, published in JEB. Luis is a PhD student in the lab of Timothy Clark at School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia, investigating thermal effects on the cardiorespiratory oxygen supply in fish.
Luis Kuchenmüller
How did you become interested in biology?
My family always prioritised being in nature. Traveling to the Aegean Sea and the Galapagos Islands at an early age sparked my wish to learn about marine wildlife. Snorkelling was my favourite thing as a child, and I spent as much time as I could underwater. To this day, setting out to explore reef communities, getting to know the ecosystems and where to reliably find brittle stars and octopuses is one of my favorite activities. Then, in high school, my curiosity in biology was forged by being educated on human-made climate change. Feeling helpless about it ultimately led me to pursue a career in marine science.
Describe your scientific journey and your current research focus
After a bachelor's degree in biology at the University of Hamburg, I commenced a marine biology master's degree at the University of Bremen. For my final research thesis, I joined the integrative ecophysiology team at the Alfred Wegener Institute for Polar and Marine Science. Supervised by Felix Mark, I worked with a key species of one of the most rapidly changing environments on earth: polar cod. For this project, I implanted heart rate bio-loggers and ran critical swim speed tests across a temperature gradient. I also gained some analytical experience, training a machine-learning program to track swimming movements in videos taken during the critical swim speed tests and measuring tailbeat frequencies. In 2022, I moved to Australia and joined Tim Clark's ecophysiology research group at Deakin University. As a PhD student, I am studying the allometry of cardiorespiratory variables and their temperature dependence in salmonids, specifically Chinook salmon and rainbow trout. To investigate the impact of hyperoxia across a mass range, I have instrumented fish with vascular cannulas in the arterial and venous systems. Recently, I was fortunate enough to receive a COB travel fellowship, which I have used to visit Andreas Ekström at Gothenburg University. During my stay, we implanted optodes into the dorsal aorta of rainbow trout, allowing for live recordings of blood–oxygen partial pressure just behind the gills, research I am looking forward to sharing in the future.
How would you explain the main findings of your paper to a member of the public?
My research aims to contribute to our understanding of how aquatic animals take up and circulate oxygen under warming conditions caused by climate change. My focus lies in discerning whether larger fish are less capable of circulating oxygen in comparison to smaller fish of the same species, potentially making them more susceptible to aquatic heatwaves. In this paper, we showed that in our ‘heatwave treatment’, bigger rainbow trout were less capable of processing oxygen to fuel their metabolism compared with smaller individuals (relative to how we know oxygen demands to increase with size). When we increased the oxygen availability in the water beyond air saturation (called hyperoxia), bigger individuals benefitted more than smaller ones, and the slope of the relationship between the fish's oxygen processing capabilities and their body masses was reestablished to what we had observed in our cold temperature treatment. In the natural environment, hyperoxia is relevant in habitats with little water flow and high amounts of photosynthesis, potentially providing important refuge for larger individuals. However, more research is necessary to determine whether this refuge only encompasses activities such as escaping predators and feeding, or whether it also benefits survival during a heatwave.
Instrumenting a rainbow trout with a cannula in the dorsal aorta.
Instrumenting a rainbow trout with a cannula in the dorsal aorta.
What do you enjoy most about research, and why?
My favorite part about research is that my day-to-day working life is multi-faceted, I regularly get to experience entirely new challenges, and I can keep on learning. If I was planning my experiments thoroughly in one week, another week I might have to improvise with my collaborators because of unexpected complications. I would run to the store for guitar wire necessary for the surgeries, or desperately try to catch a 4 kg rainbow trout from a 15,000 l water tank. Desk work can range from learning to code a new statistical analysis to collectively writing a manuscript in a Google Doc. I have also been fortunate enough to travel internationally for my work on multiple occasions where I was introduced to new colleagues who are now friends.
What is the hardest challenge you have faced in the course of your research and how did you overcome it?
Investigating mass scaling in fish did at times present me with challenges. To design experiments that allowed me to compare across sizes, I had to think about differences in fish husbandry across multiple size-specific holding tanks, how vascular surgeries would differ across size classes, and how to build various experimental set-ups and respirometers fit for mass ranges of instrumented fish. In the end, I overcame certain stages of my experiments by stubbornness and relying on my lab mates. However, writing about the research and seeing our results has been cathartic, and now I am looking forward to the next experiments to come.
What do you like to do in your free time?
My favorite thing is to explore Australia with my partner. This is a country with incredible wildlife (and the opportunity to see it), and I am fortunate enough to have seen relatively elusive animals (echidna, platypus and thorny devil). I like to go camping in Victoria's national parks, which are stunning, because I feel like the Australian tree ferns create quite a Jurassic atmosphere. I am also inspired by First Nations stories, and believe we have a lot to learn about treating the environment from these cultures that have walked the land since time immemorial.
What's next for you?
I have about one more year to finish my PhD. Afterward, I plan to drive the family caravan to the Mediterranean Sea before I begin my next research journey in a postdoctoral position. I wish to continue working experimentally in the future, focusing on climate change relevant research.
Luis Kuchenmüller's contact details: School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia.
E-mail: [email protected]