Dietary Spirulina (Arthrospira platensis) Modulates Survival, Growth, Reproductive Behavior, and Spawning Performance in Zebrafish, Danio rerio

In aquaculture and in laboratory settings, the development of sustainable and functional feeds is crucial in order to promote fish welfare, growth, and reproductive performance. Among natural dietary supplements, spirulina (Arthrospira platensis), a blue-green microalga rich in proteins, essential fatty acids, vitamins, and antioxidant molecules, represents a promising bioactive ingredient capable of influencing both physiological and behavioral traits. A 32-week longitudinal study was conducted on adult zebrafish (Danio rerio) to evaluate the effects of spirulina supplementation (5%, 25%, 50%, 75%, and 100%) compared to a standard diet. Parameters related to survival, growth, reproductive fitness, and reproductive behavior were assessed in vivo and supported by a morphometric analysis of the gonads. Supplementation with 5% improved survival rate and the Body Condition Index, while 25% supplementation increased survival, enhanced reproductive behavior and spawning success (140% egg production vs. control), and supported optimal gonadal development and gamete maturation timing. Higher percentages of spirulina (50–100%) seem to cause nutritional imbalance, impairing health and reproductive fitness. This study demonstrates that moderate spirulina supplementation (5–25%) supports health, reproductive physiology, and behavior in zebrafish in a dose-dependent manner. These results highlight the potential of spirulina as a functional supplement for precision nutrition approaches, with implications for fish welfare, reproductive performance, and aquaculture sustainability.