Taurine supplementation improves the resistance of Crassostrea gigas larvae against Vibrio splendidus invasion

In the past decade, high larval mortality due to pathogenic bacterial infections has severely constrained the oyster industry in China. It is crucial for seeking an immunopotentiator to improve the larval resistance and address the high mortality. This study investigated taurine as a potent immunopotentiator to enhance the growth performance and immune capability in Crassostrea gigas larvae. On the 10th day after the treatment of 10⁻⁷ mol/L taurine, the shell height and shell length of larvae were 1.11- and 1.09-fold of those in the control group (273.17 μm, 255.78 μm). The taurine-treated larvae showed a higher survival rate (85.33%) against Vibrio splendidus compared to the control group (61.21%), as well as a 3.14-fold higher eyespot occurrence rate. After the taurine treatment, the mRNA expression of insulin-like peptide receptor (ILPR), insulin-like growth factor binding protein-related protein (IGFBPRP), extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MAPK), mammalian target of rapamycin (mTOR), S6 kinase (S6K), and rhodopsin-like gene (CGI_10012534) significantly increased, which were 2.15-fold (p < 0.01), 1.72-fold (p < 0.001), 2.25-fold (p < 0.01), 2.55-fold (p < 0.01), 1.67-fold (p < 0.05), 3.38-fold (p < 0.01), and 29.05-fold (p < 0.001) of those in the control group, respectively. And the mRNA expression of superoxide dismutase (SOD) and catalase (CAT) also significantly increased compared to the control group. These results suggest that taurine treatment improves the larval resistance by activating the insulin/MAPK-mTOR and the antioxidant pathways, which provides an effective and eco-friendly solution to hatchery success of oyster.