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Fig. 10 | BMC Ecology and Evolution

Fig. 10

From: Three in one: evolution of viviparity, coenocytic placenta and polyembryony in cyclostome bryozoans

Fig. 10

Details of larval and gonozooid structure in Crisia eburnea (a, h) and Crisiella producta (bg) (a, b, light microscopy, ch, TEM). a, b Oblique section of gonozooid showing secondary embryos and early larvae embedded into the nutritive tissue (folded cuticular area of the larval apical pole shown by arrowheads). c Part of bilayered secondary embryo with central cavity, peripheral columnar and flattened ‘inner’ cell lining. d Apical part of early larva with cuticular ‘cap’ (asterisks) (arrows show granules with ‘striated’ content). e Part of early larva with folded cuticular ‘cap’ (asterisks). f Elongated cells of the larval adhesive sac with numerous round inclusions and more peripheral cells with ‘fine-grained’ content (arrowheads). Electron-dense lipid droplets are visible in embryonic and larval cells. g ‘Upper cell complex’ filling space between gonozooid wall (lower left corner) and the roof of membranous sac (not shown); folded cuticular wall of remained vestibulum shown in insert. h Cross-section of the uppermost part of folded roof of coenocytic membranous sac surrounded by thick basal lamina (arrowheads) and ‘upper cell complex’. ao, adhesive organ of larva; b, bilayered secondary embryo; cw, external cystid wall; la, early larva; m, morula-like secondary embryo; nt, nutritive tissue; pc, pseudocoel; rm, roof of membranous sac; sc, storage cells; uc, ‘upper cell complex’

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