The Potential of Zebrafish Larvae and Water Vortex Protocols in Stress Biology

Stress responses enable vertebrates to adapt to environmental challenges while maintaining homeostasis. Zebrafish larvae are a valuable model for studying stress regulation due to their genetic accessibility and rapid development. This review examines the integration of zebrafish larvae with water vortex protocols to investigate hypothalamic–pituitary–interrenal (HPI) axis functionality during early development, advancing stress research while adhering to the 3Rs principle. Key publications are reviewed to discuss the potential of water vortices in zebrafish larvae for studying stress responses. These purely physical stressors exploit the innate positive rheotropism of developing zebrafish, offering precise control over timing and strength while avoiding confounding factors associated with chemical or biological interventions. The approach enables reproducible assessments of stress responses. The reviewed publications show advances in understanding cortisol response dynamics, glucocorticoid feedback, and early-life stress-induced changes in HPI axis function. Key findings include detailed cortisol patterns after acute stress, rapid glucocorticoid receptor-mediated feedback regulating cortisol levels, developmental shifts in HPI axis sensitivity, and reduced cortisol reactivity following early-life challenge (ELC). Vortex-driven ELC affects cortisol regulation, neuropeptide expression in the nucleus preopticus, and stress-related gene transcription. Combining zebrafish larvae and vortex protocols provides a robust and innovative platform for investigating stress biology. This approach leverages active, demanding behaviour to study stress mechanisms under controlled conditions, yielding insights with broad applications across vertebrate models while supporting the 3Rs principle. Future studies can build on these findings to address unresolved questions in stress regulation and enhance our understanding of adaptive physiological mechanisms.