Figure 1.

The stem cell system of Isodiametra pulchra (A, B). Morphology (C-E), distribution (F-I), and differentiation (J-L) of neoblasts. (A) Schematic drawing. (B) Differential interference contrast image. (C) Typical neoblast with nucleus (red) and thin rim of cytoplasm (yellow). (D-D") Macerated BrdU labelled cells show typical neoblast like morphology (E) BrdU labelled neoblast, as shown by immunogold staining after a 30 min BrdU pulse; arrowheads point to gold particles (F) histological cross section; brown spots are BrdU labelled S-phase cells. (G, H) Confocal projection overview (G) and detail of lateral body margin (H) after 30 min BrdU pulse; the red spot in (H) is a mitotic figure. Note that S-phase cells were lacking in the epidermis (between dotted lines). (I) Electron microscopic image of a posterio-lateral body margin. (J) Histological section, 10 days after the initial BrdU pulse. Some of the neoblasts underwent differentiation into epidermal cells (arrows); (K) BrdU labelled cells, differentiated after 10 days chasing time. Differentiating spermatid (top left), epidermal cells (top middle), parenchymal cell (top right), nerve cells (bottom left), and a muscle cell (bottom right) (L) BrdU labelled differentiated epidermal cell after 10 days chasing; arrowheads point to gold particles. bwm, body wall musculature; c, cilium; cc, condensed chromatin; cs, central syncytium; d, diatoms; e, egg; de, developing eggs; ep, epidermis; g, golgi; m mitochondria; mo, mouth opening; n nucleolus; st, statocyst; tw, terminal web. Scale bars (A, B, G) 100 μm; (C, E, L) 1 μm; (D, H; K) 10 μm; (F, J) 25 μm; (I) 5 μm.