ECR Spotlight – César Bertinetti Free

César Bertinetti

How did you become interested in biology?

I have always been drawn to nature. I grew up in the countryside, where playing in the forest was our main form of entertainment. A few key moments also helped shape my current interests. When I was seven, I received a kids' microscope as a Christmas gift and spent hours trying to look at insects, flowers, pinecones – pretty much anything I could collect outdoors (though not always with much success!). Around the same time, I became fascinated by a VHS collection of National Geographic documentaries my parents owned. In high school, I drifted away from biology a bit, since it was not really seen as a viable career path in my context. But as an undergraduate, I had my first fieldwork experiences, and that completely changed my perspective. I signed up for a trip to Brittany to study seaweeds, and later joined a rainforest expedition in Taiwan as a field assistant. Those trips showed me how much I enjoyed working with living organisms in their natural environments. Another pivotal moment came when my current advisor showed me an image of a stained fish retina. I did not have a strong background in molecular biology at the time, but seeing the photoreceptor cells and the spatial patterns of opsin gene expression completely blew my mind. It connected the beauty of biology at the molecular level with my fascination for how animals interact with their environments.

Describe your scientific journey and your current research focus

My first research experience was working with insects. As a biology undergraduate at the University of Konstanz in Germany, I had the opportunity to spend a year in a lab exchange program at National Chung Hsing University in Taichung, Taiwan. There, I worked with Prof. Shaw-Yhi Hwang and his student Ana Samayoa on a project studying how different diets affect life-history traits in black soldier flies (Hermetia illucens). When I returned to Germany, I wanted to continue working with insects and became interested in beekeeping. This led to my bachelor's thesis with Morgane Nouvian, where I explored the neuroethology of stinging behavior in honeybees. For my master's degree, I stayed in Konstanz but shifted my focus to fish – specifically, neotropical cichlids and their visual systems. I was fortunate to join a big research group, where researchers used a wide range of methods. Being part of such an interdisciplinary group exposed me to molecular and genomic techniques as well as ecological and behavioral research. That experience shaped my current research focus: understanding the mechanisms and consequences of variation in visual traits in fish. I am particularly interested in how environmental and developmental factors influence vision and how these changes, in turn, affect behavior and evolution.

How would you explain the main findings/message of your paper to a member of the public?

Fish live in very different environments – water can look crystal clear in the ocean or murky in a swamp. These big differences in how far fish can see underwater affect important tasks like finding food or avoiding predators. Some of the key molecules that influence how animals see color are visual pigments. These are found in special cells in the eye and rely on proteins called visual opsins. Each opsin responds best to a specific color of light, so most vertebrates see color by using a mix of opsins. Humans use three opsins to see color, but fish are much more diverse. Their vision varies widely, likely because they live in so many types of habitats. Since scientists developed tools to study gene activity, many have focused on whether fish can change which opsins they use depending on their environment. For example, sunlight can change daily or seasonally, and underwater light can shift quickly due to algae or stormwater. Many studies have found that fish vision, and opsin gene expression in particular, is flexible and can vary during an individual's lifetime. We thought this ability of fish to tune their vision in response to stimuli deserved closer study. So we gathered all the available research on this topic across many species of bony fish to look for general patterns. We found that flexibility in opsin use is common in fish and these gene expression changes can be strong. By combining all the studies in a meta-analysis, we were able to discover general patterns beyond individual studies. For instance, we found that fish exhibiting stronger plasticity in opsin gene expression do not always resemble their close relatives, suggesting that this trait may evolve quickly. We also found that different opsins respond to different triggers: those detecting ultraviolet light changed most during development in response to light, while those tuned to red light responded more to hormonal stimuli. Overall, our study highlights what is known – and what still is not – about how and why fish change their vision, and what we need to do to better understand this fascinating biological trait.

Why did you choose JEB to publish your paper?

JEB has a long-standing reputation for publishing high-quality research in sensory biology and visual ecology, so it felt like a natural fit for our manuscript. I also deeply value society-led journals and their commitment to serving both the scientific community and the wider public in a not-for-profit context. Personally, it's an honor to publish in JEB and contribute in a small way to the mission of The Company of Biologists. I find many of the society's initiatives to be genuinely supportive of the academic community. For example, the Early-Career Researcher Spotlights are a great way for young scientists like me to build visibility and connect with a broader audience. The Read & Publish agreement with my current institution was another factor I considered when choosing a journal. I also really admire the society's creative and community-driven efforts, like the workshops they offer and initiatives such as The Forest of Biologists. And I was excited to see that they've even sponsored episodes of Big Biology – my favorite podcast!!

What do you enjoy most about research, and why?

I am a naturally curious and active person – new questions and ideas are constantly running through my mind, and I tend to get bored if I have to repeat the same task over and over. That's why science, and especially my work in molecular ecology and evolution, suits me so well. It allows me to regularly switch between different tasks and systems. I really enjoy the variety in my work: spending time in the field, running behavioral experiments with live fish, performing molecular protocols in the lab, and analyzing sequencing data with bioinformatic tools. Taking an integrative approach to research – one that tackles questions from multiple angles – can sometimes be frustrating, as it demands learning new skills and managing different types of data. But for me, that variety is exactly what makes this job so exciting and fulfilling.

What is your favourite animal, and why?

This one's easy: fish – more specifically, cichlid fishes (Cichlidae). Cichlids are fascinating in so many ways. They show remarkable biological diversity, yet their evolution seems to follow certain ‘rules’ that allow us to draw inferences at both micro- and macroevolutionary scales. I truly believe that for almost any ecological or evolutionary hypothesis you can think of, there is a cichlid system that could help test it. Cichlids have made major contributions to our understanding of adaptive radiations, speciation, sensory ecology, molecular evolution, behavior, and broader ecological theory. And beyond their scientific value, they are simply captivating animals. Anyone who has seen colorful cichlids caring for their fry – or has scuba-dived into their underwater world – can appreciate their beauty and complexity.

What's next for you?

Most of my research so far has focused on cone photoreceptor cells in the fish retina and how the expression of visual opsin genes contributes to adaptation across different aquatic habitats. While we have a fairly good understanding of how opsin gene expression relates to the visual pigments used in color vision, color perception itself is much more complex. It involves more than just detecting light at different wavelengths – there are many downstream processes in the retina and brain that shape how animals perceive and respond to light. In the future, I am excited to explore these downstream pathways and investigate how gene expression influences neural processing, ultimately affecting visual perception and behavior. Ideally, I would love to keep working on cichlid fish retinas – just dive a bit deeper into their brain.