Altitude-Related Adaptation in Freshwater Snails (Cipangopaludina cathayensis): Insights from Biochemical, Transcriptomic, and Metabolomic Analyses

High-altitude environments expose aquatic organisms to complex environmental challenges, including fluctuations in dissolved oxygen levels, water temperature, and other habitat conditions. The freshwater snail Cipangopaludina cathayensis has limited dispersal ability and is strongly associated with local habitat conditions, making it a suitable species for investigating biological responses to long-term environmental variation. In this study, high-altitude and low-altitude populations of Cipangopaludina cathayensis were compared using biochemical assays, shell elemental composition analysis, transcriptomics, and metabolomics to explore altitude-associated physiological and molecular responses. Environmental monitoring showed that the high-altitude habitat exhibited lower water temperatures, greater thermal variability, and significantly higher dissolved oxygen availability than the low-altitude habitat, indicating distinct environmental conditions between the two populations. The high-altitude population exhibited significantly higher superoxide dismutase (SOD) and pyruvate kinase (PK) activities than the low-altitude population, whereas malondialdehyde (MDA) content and total ATPase (T-ATPase) activity showed no significant differences between populations. Shell microstructure and elemental analyses revealed altitude-associated differences in biomineralization. Transcriptomic analysis identified differentially expressed genes involved in intracellular transport, including KIF10, KIF11, KIF13, KIF17, MYO3, and MYO7A, as well as apoptosis-associated genes, including CASP2, CASP3, and BCL-2. Integrated transcriptomic and metabolomic analyses further highlighted purine metabolism, D-amino acid metabolism, insulin resistance, and alanine, aspartate and glutamate metabolism as shared enriched pathways between the two populations. These findings indicate that Cipangopaludina cathayensis may cope with high-altitude environments through coordinated regulation of antioxidant defense, intracellular transport, apoptosis-associated pathways, and metabolic homeostasis.