# Dietary Escitalopram Reduces Movement Variability and Enhances Behavioral Predictability in Drosophila melanogaster

## TL;DR

Feeding fruit flies escitalopram reduces individual differences in movement behavior, making their actions more predictable.

## Contribution

This study shows that developmental dietary exposure to escitalopram reduces behavioral variability in fruit flies.

## Key findings

- Flies exposed to escitalopram showed reduced turning behavior variability compared to controls.
- Tryptophan supplementation did not significantly affect behavioral variability in fruit flies.

## Abstract

Animals often differ consistently from one another in how they behave, a phenomenon known as behavioral individuality. Such differences can be important for how animals cope with changing or risky environments. In this study, we examined whether long-term dietary exposure to two commonly used compounds, tryptophan and escitalopram, is associated with differences in behavioral variability in fruit flies (Drosophila melanogaster). Flies were reared on food containing either tryptophan, escitalopram, or control food, and their movement decisions were later measured in a Y-shaped maze. We found that flies exposed to escitalopram showed reduced variation among individuals in turning behavior, resulting in more predictable movement patterns, whereas tryptophan exposure was not associated with consistent changes in behavioral variability. These findings indicate that chronic exposure to escitalopram during development is associated with altered patterns of behavioral individuality in fruit flies.

Behavioral individuality, often termed animal personality, reflects consistent patterns of behavioral variability across individuals. In fruit flies (Drosophila melanogaster), pharmacological and dietary manipulations affecting neuromodulatory systems have been shown to alter behavior, but their effects on behavioral predictability remain incompletely understood. Here, we investigated whether developmental dietary exposure to tryptophan (a serotonin precursor) or escitalopram (a selective serotonin reuptake inhibitor, SSRI) is associated with changes in lateralized turning behavior. Flies were reared from larval stages on supplemented media and tested in a Y-maze assay to assess movement predictability. Flies exposed to escitalopram displayed significantly reduced behavioral variability compared to controls, indicated by a lower median absolute deviation (MAD) of turning behavior, whereas tryptophan supplementation did not significantly affect variability. Because both compounds were tested at a single dietary dose and serotonergic activity was not directly measured, these findings should be interpreted as dose-specific behavioral effects rather than evidence of altered serotonergic tone or mechanism. Our results demonstrate that chronic developmental exposure to escitalopram is associated with increased behavioral predictability in fruit flies, highlighting the utility of high-throughput behavioral assays for detecting subtle pharmacologically induced changes in individual variability. Future studies incorporating dose–response designs and physiological validation will be required to establish underlying mechanisms.