Replacing Fish Meal with Spirulina (Arthrospira platensis): Nutrigenomic Modulation of Growth, Reproductive Performance, and Metabolism in Zebrafish

Protein-rich microalgae have been increasingly recognized as viable alternatives to fish meal (FM) in aquaculture diets. In this study, we evaluated the effects of partial or total replacement of FM with the microalga <i>Arthrospira platensis</i> (Spirulina, SM) on the growth performance, reproductive parameters, and transcriptomic profile of zebrafish. Six isoproteic, isoenergetic experimental diets were formulated with increasing levels of SM (0, 10, 20, 30, 40, and 50 g kg^-1 feed) replacing FM. Fish were randomly assigned to six groups (five replicates each) and fed for 60 days. The diet containing 50 g kg^-1 SM resulted in the highest final body weight, weight gain, specific growth rate, and protein efficiency, as well as increased gonadosomatic index, eggs per female, fertilization rate, and hatching rate compared to the results for the control group (0 g kg^-1 SM). RNA-Seq transcriptomic analysis identified 2299 differentially expressed genes in the SM50 group, mainly associated with muscle development and energy metabolism. These findings offer new insights into the underlying molecular mechanisms and underscore the potential of Spirulina as a sustainable alternative for cultured fish nutrition.