부산대학교 도서관

Despite being one of the bilaterians, the body plan of echinoderms shifts from bilateral symmetry to five-fold radial, or pentaradial symmetry during embryogenesis or their metamorphosis. While the clarification of the developmental mechanism behind this transition will be a basis for understanding their unique body plan evolution, it is still poorly understood. With this regard, the hydrocoel, a mesodermal coelom formed on the left side of bilateral larva, would be a clue for understanding the mechanism as it is the first pentaradial structure that appears before metamorphosis and develops into the water vascular system of adults. By analyzing the development of a sea cucumber, Apostichopus japonicus , we found that the hydrocoel expresses genes related in muscle and neural formation such as myosin heavy chain , tropomyosin , soxC, and elav , implying that cells of the hydrocoel contributes to muscle and neural structures in the adult. Furthermore, ablation of one of the hydrocoel lobes led to incomplete development of adult pentameral structures. The ablation of primary hydrocoel lobes resulted in the reduction in tentacles and the ablation of secondary hydrocoel lobes resulted in the reduction in water vascular canals and nerve cords. Our findings suggest that the hydrocoel lobes may serve as a potential organizing center for establishing the pentaradial body plan in echinoderms. [Display omitted] • The origin of cells that form adult structures in a sea cucumber was investigated. • The hydrocoel is suggested to supply adult nervous and muscular cells. • Laser-ablation of a hydrocoel lobe causes incomplete formation of pentamery. • The hydrocoel may act in organizing the pentaradial adult structures. [ABSTRACT FROM AUTHOR]