LC-PUFA Biosynthesis in Aquatic Animals: A Hybrid Bibliometric and Thematic Review

Long-chain polyunsaturated fatty acids (LC-PUFAs) are essential to the nutrition, metabolism, and physiological performance of aquatic animals. This hybrid review combines bibliometric analysis with focused thematic synthesis to examine three decades (1991-2025) of research on LC-PUFA biosynthesis in aquatic species. Bibliometric trends reveal rising publication output and an expanding research focus on biosynthetic pathways, regulatory mechanisms, and molecular control of LC-PUFA production, with emerging emphasis on metabolomics, environmental regulation, microalgae-derived ω-3 sources, and gene-editing technologies. Thematic analysis reveals that LC-PUFA dynamics are governed by interactions among primary production, trophic transfer, endogenous biosynthetic capacity, and environmental conditions. Marine primary producers serve as major sources of EPA and DHA, whereas freshwater and terrestrial systems often exhibit greater ALA availability and higher n-6/n-3 ratios, influencing LC-PUFA transfer efficiency and consumer adaptation. The review further highlights that aquatic animals have evolved diverse endogenous biosynthetic strategies, including lineage-specific modifications of desaturase and elongase pathways, enabling adaptation to contrasting nutritional environments. LC-PUFA transport across aquatic-terrestrial boundaries through organisms such as emergent insects and amphibians represents an important pathway for transferring essential fatty acids to terrestrial food webs. Furthermore, variation in n-3 LC-PUFA availability contributes to habitat selection and evolutionary diversification, with freshwater environments promoting enhanced biosynthetic capacity through mechanisms such as Fads2 gene duplication. Future directions include structural characterization of biosynthetic enzymes via cryo-electron microscopy and AI-assisted modeling, multi-omics and genome-editing strategies for genetic improvement, and sustainable production approaches including microalgae- and insect-based feeds and integrated multitrophic aquaculture.