Tapping Chlorella vulgaris potential for enhanced growth, immunity, digestion, microbiota, and immunometabolism in Litopenaeus vannamei feeding across varied salinities

Abstract

This study explored the use of Chlorella vulgaris (CHL) in Litopenaeus vannamei under varying salinity conditions. Juvenile L. vannamei (initial weight 0.38 ± 0.01 g) were fed experimental diets for 8 weeks at different salinity levels: low (15‰), moderate (30‰), and high (45‰). The control diet contained 589 g/kg fishmeal (FM) as the sole protein source, while experimental diets included 150 g/kg FM and 492 g/kg CHL as protein sources. Results revealed that shrimp fed with CHL showed a robust survival rate even at higher salinities. Following a Vibrio parahaemolyticus infection challenge, shrimp fed with CHL exhibited higher survival rates than those fed with FM at equivalent salinities. Enzyme activity and gene expression analyses indicated that CHL enhanced immune response and digestion in L. vannamei compared to the FM, even under similar salinity conditions. Additionally, shrimp fed with CHL outperformed those fed with FM under varying salinity stress. Microbiota analysis revealed increased diversity and beneficial bacteria in the intestines of shrimp fed with CHL at the same salinity levels. Transcriptomic sequencing identified genes with differential expression (DEGs) related to immune and metabolic pathways. Furthermore, a combined analysis of microbiota and DEGs revealed that CHL also had a beneficial impact on the composition of the intestinal microbiota and controlled the expression of genes related to immune and metabolic pathways. In summary, CHL as a primary protein source improved survival rate, disease resistance, immune response, and digestion in L. vannamei, positively impacting intestinal microbiota and gene expression, and enhancing adaptability to salinity changes.