Elucidating the Evolution of Endothermy through an Endolymphomics Approach

Endothermy, the ability to maintain a stable internal body temperature, is a key evolutionary steppingstone that allows animals to thrive in diverse environments, sustain high activity levels, and achieve greater reproductive success despite increased energy demands. This thermoregulatory strategy has led to complex behaviors and evolutionary innovations, enabling endothermic animals, like birds and mammals, to dominate ecosystems throughout time. However, the origins of endothermy remain hotly debated. The ENDOMICS project aims to contribute to this debate by exploring the evolution of endothermy through advanced metabolomics and proteomics analyses of endolymph across various species. Endolymph, a fluid in the inner ear that monitors head movements and allows hearing, appears to vary in viscosity between taxa, detrimentally impacting ear biomechanics. By studying the proteins and metabolites in endolymph, we can understand the factors behind these variations. For instance, birds seem to have adapted to higher body temperatures by altering the chemical composition of endolymph, increasing its viscosity. We hypothesize this change to be linked to augmented presence of proteins/metabolites, known to increase biofluids’ viscosity, offering a cornerstone piece of information for understanding the onset and evolution of endothermy. ENDOMICS trailblazes the study of variation in the composition of endolymph across taxa. Our findings will clarify the fossil record, providing a deeper understanding of extinct species' biology by estimating their physicochemical properties from living counterparts. The study's results also have broad implications, including informing climate change adaptation, advancing treatments for hearing/balance disorders, and fostering innovation in synthetic biology, particularly with synthetic endolymph. As the global population ages, this research will be increasingly important in addressing the growing incidence of hearing impairments.