Shrimp farming can suffer from significant economic losses due to diseases. Stress factors like water quality and weather changes , transportation, and stocking can cause disease outbreaks , so improving shrimp natural defenses is crucial. Seaweed extracts have recently been investigated as a natural tool due to its ability to enhance gut barrier function and modulate immune responses in aquatic animals. Field trials have demonstrated improved survival rates in shrimp challenged with major pathogens when fed with these bioactive compounds. To further evaluate the underlying molecular mechanisms, the University of the Philippines Visayas conducted a trial measuring the effects of seaweed extract on farmed shrimp gene expression.
An algae-based marine sulphated polysaccharides (MSP) extracts, from green Ulva sp . and red Solieria chordalis were used. Shrimp were assigned to two groups Control and Algae MSP 0.3% which was included before extrusion (three replicates ), which were raised for 114 days. Growth parameters were weekly recorded, and mortality was recorded daily. Immune-related gene expression at 30 and 60 days after feeding was evaluated. Briefly, samples of hepatopancreas (local immune response) and hemolymph (systemic immune response) were collected and evaluated using RT-qPCR (n=9 shrimp/treatment in triplicate). The study focused on four key immune parameters: Anti-lipopolysaccharide factor (ALF), Crustin, Penaeidin, and Prophenoloxidase (proPO). Statistical analyses were performed using SAS software in which growth results were analyzed by one-way ANOVA and F test; and gene expression by non-parametric Kruskal-Wallis test, p<0.10.
Shrimp fed the Algae MSP 3kg/T had significant modulation of the immune parameters , including the immune response in hepatopancreas after 30 days (Heat shock proteins and Crustins) and initiates the Phenoloxidase cascase in the hemolymph. HSP90 increased 500% (p=0.05) and Crustin was expressed 100% higher (p<0.05) . After 60 days, the immune response is fully orchestrated in hemolymph; and in the hepatopancreas: proPO and ALF are upregulated while Peinaedins are downregulated. Specifically , proPO at DOC 60 was 340% higher in the hepatopancrease (p=0.05) and 1172% higher in the hemolymph (p=0.05), respectively. Similarly, e xpression of ALF increased by 75 % in the hemolymph (p=0.05 ) and by 158% in hepatopancrease (p<0.05).
These results highlight the potential use of red and green algae extracts as a natural, sustainable strategy for enhancing shrimp health, regulate gene expression correlated with improved survival, and contributing to the long-term sustainability of shrimp aquaculture.