Microalgae-Derived Bioactives as Immunonutrients in Litopenaeus vannamei Aquaculture: Mechanisms, Efficacy, and Future Prospects

Shrimp aquaculture, particularly the farming of Litopenaeus vannamei, has experienced rapid growth over the past two decades. However, this intensification is frequently challenged by disease outbreaks, environmental stressors, and the overuse of antibiotics, which have raised serious concerns regarding antimicrobial resistance (AMR) and environmental degradation. Immunonutrition—the strategic use of functional dietary components to modulate immune responses—has emerged as a sustainable alternative to conventional chemotherapeutic interventions. Among various immunonutrients, microalgae have gained increasing attention due to their rich profile of bioactive compounds, including polyunsaturated fatty acids (PUFAs), pigments such as astaxanthin and fucoxanthin, sulfated polysaccharides, vitamins, and antioxidant peptides. This review highlighted the immunomodulatory mechanisms and efficacy of microalgae-derived compounds in enhancing the innate immune response of L. vannamei, including increased phenoloxidase activity, total hemocyte count (THC), and the expression of key immune genes. Comparative insights with other immunonutrients, including probiotics, β-glucans, phytogenics, and vitamins, were provided to position microalgae as a multifunctional and promising solution. Finally, current limitations and future directions for the development, application, and commercial integration of microalgae in shrimp aquafeeds were discussed. This review underscores the potential of microalgae-based immunonutrition to support disease-resilient and environmentally responsible shrimp aquaculture.