Glutamine enhances Pacific oyster (Crassostrea gigas) larval development through CgEAAT1-cortisol-CgIGF1 signaling pathway

Glutamine (Gln) represents an important functional amino acid for aquatic animals, but its regulatory mechanism in mollusk growth and development remains unclear. In the present study, Gln incubation significantly increased feeding rate (30–32 %) and metabolic activity in adult oysters ( Crassostrea gigas ), with hemocyte mitochondria exhibiting typical metabolically active states. Metabolomic analysis revealed that Gln functioned through inhibition of cortisol synthesis pathways. Corticosterone and cortisol levels decreased by 30 % and 34 % after Gln incubation, while Cg IGF1 expression increased 2.9-fold. Corticosterone content in hemocytes increased from 110 to 135 μmol/L following Cg EAAT1 interference, while cortisol increased from 400 to 460 μmol/L. Cg IGF1 expression decreased to 8 % of control levels at 24 h post-interference. Exogenous Gln supplementation reversed these effects, reducing corticosterone to 90 μmol/L and restoring Cg IGF1 expression to 2.2-fold of control. During larval cultivation, 10⁻⁶ mol/L Gln incubation significantly improved growth rate, eyespot formation rate (35 %), and settlement rate (75 %), accompanied by downregulation of Cg 11β-HSD1 expression (1.5-fold) and upregulation of Cg IGF1 expression (2.8-fold). These results indicate that Gln improves oyster larval survival and settlement via the Cg EAAT1-cortisol- Cg IGF1 pathway, providing theoretical basis for optimizing nutritional strategies in oyster seed cultivation. • Glutamine enhances Pacific oyster growth through Cg EAAT1-mediated cellular uptake and metabolic activation. • Glutamine suppresses cortisol synthesis by inhibiting 11β-HSD1 thereby upregulating IGF1 expression. • The Gln- Cg EAAT1-cortisol-IGF1 axis is conserved in both adult oysters and larvae. • Glutamine (10⁻⁶ mol/L) enhances larval growth rate, eyespot formation, and settlement success.