Studies on cell atlas in marine invertebrates provide a better understanding of cell types, stem cell maintenance, and lineages of cell differentiation. To investigate the molecular features of various cell types in molluscan muscles, we performed single-cell RNA sequencing (scRNA-seq) to map cell types in scallop adductor muscles. We uncovered the cell type-specific features of 20 cell clusters defined by the expression of multiple specific molecular markers. These cell clusters are mainly classified into four broad classes, including mesenchymal stem cells, muscle cells, neurons, and haemolymph cells. In particular, we identified a diverse repertoire of neurons in the striated adductor muscle, but not in the smooth muscle. We further reconstructed the cell differentiation events using all the cell clusters by single-cell pseudotemporal trajectories. By integrating dual BrdU-PCNA immunodetection, neuron-specific staining and electron microscopy observation, we showed the spatial distribution of mesenchymal stem cells and neurons in striated adductor muscle of scallops. The present findings will not only be useful to address the cell type-specific gene expression profiles in scallop muscles, but also provide valuable resources for cross-species comparison of marine organisms.

对海洋无脊椎动物细胞图谱的研究有助于更好地了解细胞类型、干细胞维持和细胞分化谱系。为了研究软体动物肌肉中各种细胞类型的分子特征，我们进行了单细胞RNA 测序(scRNA-seq) 绘制扇贝内收肌中的细胞类型图。我们揭示了由多个特定分子标记的表达定义的 20 个细胞簇的细胞类型特异性特征。这些细胞簇主要分为四大类，包括间充质干细胞、肌肉细胞、神经元和血淋巴细胞。特别是，我们在横纹内收肌中发现了多种神经元，但在平滑肌中没有。我们通过单细胞假颞叶轨迹使用所有细胞簇进一步重建细胞分化事件。通过整合双BrdU-PCNA免疫检测、神经元特异性染色和电镜观察，我们展示了扇贝横纹内收肌中间充质干细胞和神经元的空间分布。