Department of Evolutionary Biology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.
Koltzov Institute of Developmental Biology of the Russian Academy of Sciences, Moscow, Russia.
PeerJ. 2022 May 18;10:e13361. doi: 10.7717/peerj.13361. eCollection 2022.
(Scyphozoa, Cnidaria) is an emblematic species of the jellyfish. Currently, it is an emerging model of Evo-Devo for studying evolution and molecular regulation of metazoans' complex life cycle, early development, and cell differentiation. For , the genome was sequenced, the molecular cascades involved in the life cycle transitions were characterized, and embryogenesis was studied on the level of gross morphology. As a reliable representative of the class Scyphozoa, can be used for comparative analysis of embryonic development within Cnidaria and between Cnidaria and Bilateria. One of the intriguing questions that can be posed is whether the invagination occurring during gastrulation of different cnidarians relies on the same cellular mechanisms. To answer this question, a detailed study of the cellular mechanisms underlying the early development of is required.
We studied the embryogenesis of using the modern methods of light microscopy, immunocytochemistry, confocal laser microscopy, scanning and transmission electron microscopy.
In this article, we report a comprehensive study of the early development of from the White Sea population. We described in detail the embryonic development of from early cleavage up to the planula larva. We focused mainly on the cell morphogenetic movements underlying gastrulation. The dynamics of cell shape changes and cell behavior during invagination of the archenteron (future endoderm) were characterized. That allowed comparing the gastrulation by invagination in two cnidarian species-scyphozoan and anthozoan . We described the successive stages of blastopore closure and found that segregation of the germ layers in is linked to the 'healing' of the blastopore lip. We followed the developmental origin of the planula body parts and characterized the planula cells' ultrastructure. We also found that the planula endoderm consists of three morphologically distinct compartments along the oral-aboral axis.
Epithelial invagination is a fundamental morphogenetic movement that is believed as highly conserved across metazoans. Our data on the cell shaping and behaviours driving invagination in contribute to understanding of morphologically similar morphogenesis in different animals. By comparative analysis, we clearly show that invagination may differ at the cellular level between cnidarian species belonging to different classes (Anthozoa and Scyphozoa). The number of cells involved in invagination, the dynamics of the shape of the archenteron cells, the stage of epithelial-mesenchymal transition that these cells can reach, and the fate of blastopore lip cells may vary greatly between species. These results help to gain insight into the evolution of morphogenesis within the Cnidaria and within Metazoa in general.
（钵水母纲，刺胞动物门）是水母的标志性物种。目前，它是研究后生动物复杂生命周期、早期发育和细胞分化的进化和分子调控的新兴模型。关于 ，其基因组已经测序，生命历程转变中涉及的分子级联已经被描绘，并且胚胎发生在大体形态水平上进行了研究。作为钵水母纲的可靠代表， 可用于刺胞动物和两侧对称动物之间胚胎发育的比较分析。可以提出的一个有趣问题是，不同刺胞动物的原肠胚形成过程中是否依赖于相同的细胞机制。为了回答这个问题，需要对 的早期发育的细胞机制进行详细研究。
我们使用现代的光学显微镜、免疫细胞化学、共聚焦激光显微镜、扫描和透射电子显微镜等方法研究了 的胚胎发生。
在本文中，我们报告了来自白海种群的 早期发育的综合研究。我们详细描述了 从早期分裂到浮浪幼虫的胚胎发生。我们主要关注原肠胚形成过程中的细胞形态发生运动。描述了原肠胚形成过程中（未来的内胚层）的囊胚内陷的细胞形态变化和细胞行为的动力学。这允许比较两种刺胞动物 - 钵水母纲的 和珊瑚纲的 - 的原肠胚形成过程。我们描述了胚孔关闭的连续阶段，发现 中胚层和外胚层的分离与胚孔唇的“愈合”有关。我们追踪了浮浪幼虫体节的发育起源，并描述了浮浪幼虫细胞的超微结构。我们还发现，浮浪幼虫的内胚层沿着口-肛轴由三个形态上不同的区室组成。
上皮内陷是一种基本的形态发生运动，被认为在后生动物中高度保守。我们关于推动 内陷的细胞形态和行为的数据有助于理解不同动物中形态相似的形态发生。通过比较分析，我们清楚地表明，属于不同类群（珊瑚纲和钵水母纲）的刺胞动物物种之间的内陷在细胞水平上可能存在差异。参与内陷的细胞数量、原肠胚细胞形状的动力学、这些细胞可以达到的上皮-间质转化阶段以及胚孔唇细胞的命运在物种之间可能有很大差异。这些结果有助于深入了解刺胞动物和一般后生动物的形态发生进化。
