Developmental morphology of a holothurian, Cucumaria japonica (Dendrochirota, Holothuroidea), a species with accelerated metamorphosis

摘要: Summary Development of a holothurian, Cucumaria japonica, is examined. Holoblastic radial equal cleavage results in formation coeloblastula. Gastrulation begins on the second day. It represented by an invagination and accompanied immigration mesenchyme cells marks start development vitellaria larva. The archenteron immediately divides into rudiments hydrocoel, somatocoel rudiment gut. No unified enterocoel formed. Ends hydrocoel fuse to form ring canal which five primary tentacles, canals, polian vesicle, hydroporic are right left somatocoels, then united coelomic sac, encircling ventral mesentery disappears. Thus, day 6 pentactula completely At 10 tentacles move from gives rise two derivatives: preoral anal coelomes. By end seco...