Water temperature shapes amino acid metabolism to modulate growth and development in crustacean larvae

Water temperature is a key environmental factor influencing the growth and development of crustaceans, yet the mechanisms underlying larval responses to temperature remain poorly understood. This study investigated the effects of temperature variation on holobiont interactions in larvae of the Eriocheir sinensis. Larvae were exposed to a normal temperature regime (14 °C-23 °C, CON) or a reduced temperature regime (14 °C-19 °C LT) for 14 days. Lower temperature significantly inhibited larval growth and development, as evidenced by reduced overall length, head length, dorsal spine length, and frontal spine length (P < 0.05). Biochemical analyses revealed increased alkaline phosphatase (AKP) activity but decreased levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total protein (TP), glucose (GLU), and triglycerides (TG), suggesting suppressed metabolic activity and energy utilization under low temperature. Metabolomic analysis showed pronounced metabolic reprogramming, with 557 metabolites enriched in the CON group and 802 in the LT group, mainly associated with lysine biosynthesis and degradation, arginine biosynthesis, and phenylalanine, tyrosine, and tryptophan metabolism. Temperature shifts also reshaped the larval microbiota. The relative abundances of Actinomycetota, Bacteroidota, and Thermodesulfobacteriota and several genera decreased under LT, whereas Leucothrix, Marivita, Yoonia, and Pseudoalteromonas increased (P < 0.05). Microbial functional potentials related to amino acid metabolism were significantly suppressed. Overall, these findings suggest that reduced temperature alters amino acid metabolic capacity and host-microbiota interactions, ultimately constraining the growth and development of E. sinensis larvae.