Immunomodulatory effects of cynodon dactylon (Spermatophyta, Poaceae) on juvenile mangrove crab scylla serrata (Crustacea, Portunidae)

The demand for cultured species of crustaceans as a food source has resulted in a global increase in aquaculture production. In response, the aquaculture industry continuously develops methods to improve production performance. The mangrove crab farming in the Philippines, particularly the species Scylla serrata, is a principal contributor to the economy. However, poor nutrition and diseases still threaten the industry, especially small-scale farmers. Crustaceans, which lack an immune memory, rely on their innate immune system against infection and other external stressors that negatively affect their health. The use of immunostimulants as feed additives is becoming a popular option to enhance the immune response of farmed crustaceans while achieving cost-efficient and sustainable production. The main objective of this study was to assess the potential of Cynodon dactylon (L.) Pers as an alternative source of immunostimulant for juvenile mangrove crab S. serrata. MANOVA results have shown that juvenile mangrove crabs orally supplemented with a 0.5% C. dactylon diet exhibited significantly higher nitric oxide (NO) concentration, glutathione peroxidase (GPX) activity, prophenoloxidase (proPO), and superoxide dismutase (SOD) mRNA expression levels than the basal diet group (control) (p \u3c 0.05). PCA and k – means clustering analysis presented a total variation of 71.19% and separated the basal diet group from the other treatments. In contrast, the 0.5% C. dactylon experimental group clustered with the β-glucan diet group (positive control), indicating that their responses do not differ significantly. Lastly, the correlation between the immune parameters was positively strong, particularly between NO, GPX, and proPO, which displayed significant correlations (p \u3c 0.05; p \u3c 0.01). Overall, this study confirmed the potential of C. dactylon as an alternative source of immunostimulant, based on the superior immune response of juvenile mangrove crabs fed with C. dactylon experimental diets, particularly at 0.5% concentration. The correlation of the immune parameters may also provide valuable information for streamlining available markers to screen other sources of immunostimulants and growth-promoting feed additives. Keywords: Scylla serrata, Cynodon dactylon, immunostimulant, β-glucan, PCA, innate immune system, mangrove cra