Tissue-specific lipidomic and metabolomic divergence in mature anadromous Coilia nasus along the Yangtze River migration corridor.

Reproductive migration draws heavily on somatic lipid reserves, but tissues involved in reproduction may differ in the extent to which they reflect recent physiological history. We profiled targeted lipids in muscle, liver, and ovary and untargeted muscle metabolites in 12 mature female Coilia nasus (ovarian stages IV-V) collected concurrently at Chongming (estuarine-end; n = 6) and Taizhou (freshwater mainstem; n = 6), with anadromy confirmed by otolith Sr/Ca profiles. Muscle alone showed significant global lipidomic differentiation (PERMANOVA R2 = 0.331, P = 0.039), although multivariate dispersion also differed between sites. Of 41 phosphatidylcholine species, 40 had higher abundance in Chongming and 19 met the exploratory candidate threshold; phosphatidylcholines were strongly enriched among candidate lipids (subclass enrichment FDR = 1.1 × 10-14). Of 47 targeted acylcarnitines, 43 had higher abundance in Taizhou, a pattern mirrored by 20 of 23 untargeted acylcarnitine features. N6,N6,N6-trimethyl-l-lysine was higher in Chongming (FDR = 0.010; Spearman ρ = -0.818, P = 0.0011), but this across-individual association was largely attributable to the between-site contrast and does not establish precursor-product flux. Liver showed concordant acylcarnitine enrichment, whereas ovary lacked detectable global differentiation and showed only limited differences in LPC, eicosanoid, and PE-O species. Body size and GSI did not differ, and ovarian-stage composition was balanced. Muscle therefore showed the strongest differentiation between corridor positions. These data provide a hypothesis-generating baseline, but covariation among salinity, migration distance, and population structure precludes causal attribution.