The morphogenesis of the shell field is an essential step of molluscan shell formation, which exhibits both conserved features and interlineage variations. As one major gastropod lineage, the patellogastropods show different characters in its shell field morphogenesis compared to other gastropods (e.g., the pulmonate gastropod Lymnaea stagnalis), likely related to its epibolic gastrulation. The investigation on the shell field morphogenesis of patellogastropods would be useful to reveal the lineage-specific characters in the process and explore the deep conservation among different molluscan lineages. We investigated the early shell field morphogenesis in the patellogastropod Lottia goshimai using multiple techniques. Electron microscopy revealed distinct morphological characters for the central and peripheral cells of the characteristic rosette-like shell field. Gene expression analysis and F-actin staining suggested that the shell field morphogenesis in this species predominantly relied on cell movement and F-actin dynamics, while BrdU assay revealed that cell proliferation contributed little to the process. We found constant contacts between ectodermal and meso/endodermal tissues during the early stages of shell field morphogenesis, which did not support the induction of shell field by endodermal tissues in general, but a potential stage-specific induction was indicated. Our results emphasize the roles of cell movement and F-actin dynamics during the morphogenesis of the shell field in Lo. goshimai, and suggest potential regulators such as diffusible factors and F-actin modulators. These findings reflect the differences in shell field morphogenesis of different gastropods, and add to the knowledge of molluscan larval shell formation.

中文翻译：

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pat腹足类软体动物的早期壳场形态发生主要依赖于细胞运动和F-肌动蛋白动力学。

壳场的形态发生是软体动物壳形成的必不可少的步骤，它既表现出保守的特征，又表现出谱系变异。作为一种主要的腹足纲动物，the腹足纲动物的壳场形态发生与其他腹足纲动物（例如，肺成虫腹足纲Lymnaea stagnalis）相比，表现出不同的特征，这可能与其表皮的胃胚化有关。研究腹足类动物的壳场形态发生，将有助于揭示这一过程中谱系特异性的特征，并探索不同软体动物谱系之间的深度保护。我们使用多种技术研究了trop腹足纲Lottia goshimai中的早期壳场形态发生。电子显微镜显示特征性玫瑰花状壳区域的中央和周围细胞明显的形态特征。基因表达分析和F-肌动蛋白染色表明，该物种的壳场形态发生主要依赖于细胞运动和F-肌动蛋白动力学，而BrdU分析表明，细胞增殖对该过程几乎没有贡献。我们发现在壳场形态发生的早期阶段，外胚层与中/内胚层组织之间不断接触，这通常不支持内胚层组织对壳场的诱导，但是表明了潜在的阶段特异性诱导。我们的研究结果强调了Lo运动中壳场形态发生过程中细胞运动和F-肌动蛋白动力学的作用。goshimai，并建议使用潜在的调节剂，例如扩散因子和F-肌动蛋白调节剂。这些发现反映了不同腹足动物在壳场形态发生上的差异，并增加了软体动物幼虫壳形成的知识。