Medicinal Plant-Based Immunostimulants for Sustainable Shrimp Farming: From Bioactive Compounds to Reproductive Enhancement

Abstract

The expansion of intensive shrimp aquaculture, driven by global food demand, is challenged by disease outbreaks and reliance on unsustainable practices like eyestalk ablation to induce reproduction in broodstock. This review explores the potential of medicinal plant-based immunostimulants as a sustainable alternative, with a specific focus on enhancing the reproductive performance of the Pacific white shrimp, Penaeus vannamei. We detail the complex endocrine regulation of crustacean reproduction, highlighting the roles of the X-organ-sinus gland complex, mandibular organ, and key hormones like methyl farnesoate. This foundation underscores the mechanistic drawbacks of eyestalk ablation, creating a compelling need for natural interventions. The paper then synthesizes evidence on how bioactive phytochemicals, including flavonoids, alkaloids, and sterols, can stimulate growth, immunity, and gonadal maturation. A thorough analysis of two promising plants, Melastoma malabathricum (Karamunting) and Cyperus spp., is presented. M. malabathricum, rich in lanosterol, acts as a precursor for steroid hormones, significantly accelerating ovarian development, increasing oocyte size, and elevating progesterone levels in P. vannamei. Conversely, Cyperus spp. contains methyl farnesoate, a crustacean juvenoid hormone analog, which promotes vitellogenesis, spermatogenesis, and molting, leading to advanced gonadal maturation stages and improved spawning performance. By compiling the molecular and endocrine evidence, this review positions these herbal extracts as effective, natural, and welfare-friendly alternatives to synthetic hormones and invasive techniques, offering a viable strategy to enhance reproductive efficiency and sustainability in shrimp hatcheries.