Novel Copper-Responsive Cell Subtypes in Oyster Gills: scRNA-Seq Uncovers Detoxification Strategy and Intraspecific Accumulation Variation

As a critical interface for metal hyperaccumulation, the multicellular complexity of oyster gills poses a challenge in studying their metal uptake and detoxification mechanisms. Here, we constructed the first cell atlas of oyster gills at single-cell resolution level, identifying a total of 18 cell types. Single-cell transcriptomic analysis of gills from oysters with high and low Cu accumulation revealed the cellular regulatory network underlying intraspecific differences in metal accumulation. For the first time, Cu-specific accumulating copperphilic cells in the oyster gills were identified, and a direct correlation was confirmed between copperphilic cell abundance and Cu content (R² = 0.92). Trajectory analysis of cell differentiation revealed stage-specific gene module switching in metal-related cells, in which oxidative stress responses were activated in the early phase, while ion transport regulation dominated in the mature phase. Differentiation of Cu accumulation efficiency was mainly influenced by neuroendocrine-immune cells in gills maintaining physiological homeostasis, copperphilic cells selectively silencing intercellular communication, as well as ionocyte-mediated ncWNT pathway reprogramming. These results indicate a synergistic strategy by which oyster gills with high Cu accumulation enhance stress pathways (e.g., LT/RANKL) to mitigate Cu toxicity. This study provides a single-cell framework for studying the environmental adaptation and bioaccumulation mechanisms of pollutants.