Linking physiology to behavioral individuality in Drosophila melanogaster: Methods and Mechanisms

Individuality refers to the consistent and unique patterns of behavior, temperament, and physiological traits that vary within the same species. Individual variations arise not only because of genetic predispositions, developmental experiences, and environmental influences, but these factors also act as key drivers causing varying effects across individuals due to differences in their sensitivities and life histories. However, the molecular mechanisms underlying individual differences in physiology and behavior remain difficult to study due to the intricate interactions between influencing factors, limitations in measurement and methodology, dynamic variation with high context dependency, and even ethical considerations in human research. Drosophila melanogaster has emerged as a powerful model for dissecting the origins of inter-individual differences due to its minimal genetic variability, behavioral diversity, and accessibility for tightly controlled experimental conditions. Recent advances in genetic tools and behavioral paradigms have collectively transformed our understanding of individuality at the level of single flies. In this review, we firstly discuss the determinants of variations in individual responses in Drosophila melanogaster and how these factors further amplify behavioral diversity within a population. Secondly, we summarize the current analytical approaches that allow for the precise quantification of these subtle variations in individual physiology and behavior. Finally, we highlight the translational potential of the Drosophila model for precision medicine. By shifting the analytical framework from group means to individual variance, this review provides a mechanistic roadmap for understanding the biological basis of individual idiosyncrasy.