Single-cell atlas of Exopalaemon carinicauda gills provides insights into pillar cell-mediated responses to low-salinity stress in crustaceansOA

Low-salinity stress exerts strong constraints on ion homeostasis in crustaceans cultivated in coastal environments.Gills function as central osmoregulatory organs in crustaceans,coordinating transepithelial ion flux and acid-base balance;however,the cellular mechanisms governing gill adaptation to reduced salinity remain poorly understood.Here,integrated ultrastructural characterization and single-cell RNA sequencing(scRNAseq)were applied to define cellular responses to lowsalinity exposure in Exopalaemon carinicauda gills.Low salinity induced pronounced morphological remodeling in pillar cells.Single-cell transcriptomic profiling resolved 11 transcriptionally distinct populations,including two ionocyte lineages represented by pillar cells and septal cells.Comparative analyses demonstrated a marked expansion of pillar cell subcluster 3 under low-salinity stress,accompanied by enrichment of differentially expressed genes(DEGs)in ion transport pathways,notably hydrogen ion transport.Weighted gene co-expression network analysis identified coordinated up-regulation of hub genes associated with pH regulation within pillar cells.Pseudotime reconstruction further indicated that gill adaptation to low-salinity stress proceeds through a defined differentiation trajectory(cell fate 1)originating from pillar cells.Core stress-responsive genes in pillar cells,including V(H+)-ATPases and cytoplasmic carbonic anhydrase,were predominantly associated with acid-base regulation.Collectively,these results delineate gill cellular heterogeneity and identify pillar cell-mediated regulatory mechanisms that underpin crustacean physiological adaptation to low-salinity environments.