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

## TL;DR

Adding spirulina to zebrafish diets improves their health and reproduction, but only at moderate levels.

## Contribution

The study shows that moderate spirulina supplementation improves zebrafish health and reproduction in a dose-dependent manner.

## Key findings

- Moderate spirulina supplementation (5–25%) improves survival, growth, and reproductive success in zebrafish.
- Higher spirulina levels (50–100%) impair health and reproductive fitness due to nutritional imbalance.
- Spirulina at 25% increases egg production by 140% compared to the control diet.

## Abstract

This research examined the impact of incrementally substituting a standard commercial diet with spirulina, a natural microalga renowned for its high protein and nutrient density, in zebrafish (Danio rerio). This longitudinal study aimed to assess how varying levels of spirulina integration in the diet affect fish health, growth, and reproductive success over a 32-week period. The findings revealed that while the partial substitution of commercial feed with spirulina maintained normal growth and reproduction, complete substitution resulted in poor health and decreased survival. Moreover, especially at lower substitution levels, spirulina has proven to have a beneficial effect on animal welfare and reproductive parameters. These results indicate that spirulina can be a beneficial supplement to fish diets, but the substitution levels need to be optimized to achieve the best outcomes, thereby enhancing sustainable feeding practices in aquaculture. This study underscores the potential introduction of natural ingredients like spirulina, in fostering animal welfare and also environmental sustainability in aquaculture settings.

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.