Biological Faculty, Moscow State University, 119991, Moscow, Russia.
Dokl Biol Sci. 2021 Nov;501(1):214-219. doi: 10.1134/S0012496621050021. Epub 2021 Dec 28.
The representatives of the main phylogenetic clades of Bilateria are characterized by metamery. In Deuterostomia, metamery is presented in hemichordates and chordates. Sea urchins have 7 metameric coelomic rings located along the oral-aboral axis of the body. A similar coelomic metamery is also a sign of representatives of other classes of echinoderms. We hypothesize that the metameric coelomic rings in echinoderms are inherent of the common ancestor of Deuterostomia. Asymmetry in the structure of echinoderm coeloms is the result of ancestral forms lying on the right side of the body, which led to a reduction of the coeloms on the right side. During the sedentary lifestyle, the left-side coeloms formed metameric coelomic rings.
两侧对称动物的主要进化枝代表具有分节现象。在后口动物中，分节现象存在于半索动物和脊索动物中。海胆具有 7 个体腔环沿着身体的口-肛轴排列。类似的体腔分节也是其他棘皮动物类群的代表特征。我们假设棘皮动物的体腔分节环是后口动物共同祖先所具有的。棘皮动物体腔结构的不对称性是由于祖先形式位于身体右侧，导致右侧体腔减少。在固着生活方式中，左侧体腔形成了分节的体腔环。
