Embracing variability in comparative physiology
A school of fish evading a hammerhead shark. Variations in fish’s locomotion and metabolic physiology can have a profound effect on the lifetime fitness of the individual. Biological variation matters in the face of natural selection.
The recent issue of the journal, Philosophical Transactions of the Royal Society B, compiled studies that explore the issue's theme "Embracing variability in comparative physiology: why it matters and what to do with it." Yangfan Zhang, postdoctoral researcher in Professor and Curator of Ichthylogy in the MCZ, George Lauder's lab, published two studies in the journal addressing variability that draws on his research on locomotor variation of fishes.
In the study, "A decision matrix to better identify repeatable physiological variation within individuals," Zhang and co-authors introduce Precision-&-Repeatability Assessment Matrix (PRAM), a specialized graph the team developed that plots data to help researchers distinguish between true biological differences in individuals and random experimental noise. It's crucial for scientists to know if a trait is a stable part of an animal or a random result of a one-time test, as a non-repeating trait cannot be influenced by natural selection. PRAM can help researchers see which measurements are reliable and which are influenced by noise. When tested on fish, the team discovered that aerobic (oxygen-based) measurements were more stable and precise than short-burst (non-aerobic) energy measurements, providing a better instruction manual for future research.
In the study, "Locomotor variation of fishes: connecting energetics and kinematic modulation," Zhang and co-authors investigate how fish schools move together. Instead of focusing on the average speed of a group, the team tracked the tiny, split-second changes in how individual fish flap their tails and shift positions within a school. By measuring swimming patterns and oxygen use together, they discovered that even minor shifts — like a change in the current or a fish's social rank within the school — caused a fish to instantly change its gait, thus immediately changing how much energy it burns.
Together, the two studies can help build a more accurate map of how animals move and survive in the real world, making real-time individual choices.