Reducing stress by improving performance of hatchery-reared Catarina scallop (Argopecten ventricosus) spat with different genera of beneficial microorganisms: A biochemical and molecular analysis

This study investigated the probiotic effects of one lactobacillus, one marine yeast, mix of three bacilli and mix of all probiotic strains on the growth, survival, antioxidant response (superoxide dismutase = SOD, catalase = CAT, gluthatione peroxidase = GPX) and immune response (lysozyme = LYZ, heat shock protein = HSP70) of hatchery-reared Catarina scallop Argopecten ventricosus early spat. The spat was exposed every three days for 28 days to a single dose of 1 x 10(6) CFU mL(-1) of one of five treatments used in triplicate: (1) Lactobacillus plantarum (C3); (2) Candida cretensis (S10); (3) Mix of Bacillus cereus, Bacillus fiexus, and Bacillus firrnus (BMix); (4) Mix of 1 + 2 + 3 (LLBMix); (5) Group of spat without probiotics as control. Survival was 100 % in all pro biotic treatments and the control group. The spat treated with the yeast (S10) and lactobacillus (C3) significantly increased absolute growth and growth rate compared to the control. The antioxidant activity and gene expression was significantly lower in all spat treated with probiotics than in the control group, particularly with the BMix, LLBMix (SOD), C3 (CAT, GPX), and BMix (CAT) strains. The immune activity and gene expression was also significantly lower in spat treated with probiotics, particularly BMix, LLBMix (LYZ), C3, BMix, and S10 (HSP70) strains, compared to the control group. The use of a single dose of probiotic or mix of different strains reduced activation of antioxidant and immune response and improved overall performance of hatchery-reared A. ventricosus spat