Lanthanum exposure and its metabolomic effects on Ruditapes philippinarum

The growing release of rare earth elements (REEs) into aquatic environments, driven by their extensive industrial and technological applications, has raised growing concern due to their largely unknown ecological and toxicological effects. Among these, lanthanum (La), one of the most widely used REEs, is increasingly detected in marine ecosystems. This study investigates the short-term impact of exposure on the Manila clam, Ruditapes philippinarum, a key benthic species in Mediterranean aquaculture. Clams were exposed to 10 mg/L of LaCl₃·7 H₂O, and their gill tissues were analyzed through histological examination and untargeted metabolomics. Histological analysis revealed epithelial degeneration, decreased mucus secretion, and altered glycoprotein expression following exposure. Metabolomic profiling identified 188 differentially expressed metabolites (DEMs) associated with disruptions in organic acid, fatty acid, amino acid, and nucleotide metabolism. Functional analysis of DEMs revealed that alterations in glutathione (GSH), ascorbic acid, oleic acid, and thymidine levels may serve as biomarkers of La-induced oxidative and metabolic stress in bivalves. These findings emphasize the ecological threats associated with the increasing REEs contamination in marine environments.