Embracing Variability in Comparative Physiology
From the Department of Organismic and Evolutionary Biology:
A school of giant danio Devario aequipinnatus swimming in the ‘water treadmill’ – swim-tunnel respirometer – for the measurements of the whole-animal metabolic rate while the water velocity is regulated.
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 George Lauder's lab (OEB professor and MCZ Curator of Ichthyology and Acting Curator of Herpetology), published two studies addressing variability that draw 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 examine the performance of an individual distinguished from experimental noise. The researchers propose a Precision-&-Repeatability Assessment Matrix (PRAM) to help scientists distinguish between "true" biological differences in animals and the "noise" caused by measurement errors. It is crucial for scientists to know if a trait is a stable part of the animal or is a random result of a one-time test as a non-repeating trait cannot be influenced by natural selection. By plotting data on a graph, PRAM can help researchers see which measurements are reliable and which are influenced by noise. When the team tested PRAM on fish, they discovered that oxygen-based (aerobic) 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 a group of fish move together. Rather than focus on the average speed of a fish, the team looked at the tiny, moment-to-moment changes in how fish flap their tails or change positions within a school. By measuring swimming patterns and oxygen use together they found that even small shifts in the current or social rank caused a fish to 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.