Abstract
Solute carrier family 12 (SLC12) encodes electroneutral cation-coupled chloride cotransporters responsible for transmembrane ion transport (Na(+), K(+), and Cl(-)), which play a critical role in aquatic osmoregulation. However, the SLC12 gene of Exopalaemon carinicauda (EcSLC12) has not been systematically identified or functionally characterized. In this study, six EcSLC12 genes were identified across the genome and classified into N(K)CC, KCC, CCC9, and CIP subfamilies. Three NKCC1 homologous genes (EcSLC12A2.1, EcSLC12A2.2, and EcSLC12A2.3) were reported for the first time in crustaceans. The EcSLC12 family exhibited distinct expression patterns in response to low-salinity, high-alkalinity, and saline-alkaline stress. EcSLC12A2.2 was highly expressed in the gill, and its expression was closely correlated with saline-alkaline acclimation. Additionally, EcSLC12A2.2 knockdown decreased E. carinicauda survival under saline-alkaline stress. Thus, EcSLC12A2.2 plays critical roles in osmotic regulation and saline-alkaline acclimation. This study provides crucial insights into E. carinicauda's saline-alkaline tolerance mechanisms, and the discovery of multiple NKCC1 homologs fills a gap in the crustacean SLC12 gene family research.