How Does a Freshwater Snail ( <i>Bellamya aeruginosa</i> ) Tolerate Extreme Drought in Floodplain Wetlands? Insights From Field Surveys, Biochemical Indicators and Metabolomics

ABSTRACT Molluscs are a vital component of floodplain wetland ecosystems worldwide, playing key roles in water purification and nutrient cycling. However, the increasing frequency and intensity of global droughts, particularly flash drought (FD) events, have led to widespread mollusc mortality. Bellamya aeruginosa , a dominant freshwater mollusc, has demonstrated remarkable tolerance to extreme drought (ED) conditions. Yet, the underlying mechanisms enabling drought resilience remain unclear. To bridge this gap, we combined field surveys with controlled indoor simulation experiments to assess changes in the density and biomass of B. aeruginosa before and after ED (Pre‐ED and Post‐ED), and to explore its molecular responses to drought stress. At the population level, no surviving individuals were found on the soil surface during the ED phase. However, as rewetting duration increased, the density and biomass of B. aeruginosa gradually rose and eventually recovered to pre‐ED levels. Laboratory experiments revealed that B. aeruginosa crawls into moist, shaded crevices during extreme drought, entering a dormant state by burrowing upside down with its operculum facing upward to endure harsh aridity. During the rewetting phase, its ovoviviparous reproductive strategy enables rapid population recovery. At the molecular level, drought stress led to a statistically significant change in biochemical parameters. Glycogen and protein contents, along with lactate dehydrogenase activity (LDH), were significantly elevated, whereas triglycerides (TG) and antioxidant parameters declined markedly in both the normal drought (ND) and ED groups during drought stress. Metabolomic analyses revealed that combined hypoxia and desiccation stress induced substantial shifts in metabolic pathways. Notably, metabolites involved in glycolysis, fatty acid metabolism and the tricarboxylic acid (TCA) cycle were significantly affected. Key metabolites, including Pyruvaldehyde, Carnitine, Arginine, Histidine, Sphingosine, Ile‐Pro and Acetylcholine, were downregulated, while Malate and Pantothenol were upregulated. Furthermore, metabolites related to nucleotide metabolism, such as Inosine, 2′‐deoxycytidine 5′‐monophosphate, Pseudouridine and Uracil, showed consistent downregulation with increasing drought severity. Overall, B. aeruginosa employs a combination of behavioural strategies, physiological adaptations and rapid reproductive capabilities to endure and recover from extreme drought, thereby enhancing the resistance and resilience of floodplain wetland ecosystems. These findings highlight the importance of conserving microhabitats with residual moisture and offer a scientific foundation for hydrological regulation by water management authorities. Furthermore, the findings provide critical insights into the adaptive strategies and potential evolutionary responses of freshwater organisms under future climate‐induced drought scenarios.