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Figure 2 | BMC Developmental Biology

Figure 2

From: Muscle differentiation in a colonial ascidian: organisation, gene expression and evolutionary considerations

Figure 2

Aspects of the adult blastozooid musculature of B. schlosseri. Phalloidin -FITC staining (A-C), ISH onsection (D-H; M, N) and TEM (I-L). A) Dorsal view; general organisation of musculature (arrows). Arrowhead: oral siphon. Scale bar = 0.1 mm. B) Two longitudinal fibres (arrows) accompany the dorsal lamina. (os), oral siphon. Scale bar = 50 μm. C) Cloacal siphon (cs)formed by the confluence of dorsal languets (*). Arrows: musclefibres. Scale bar = 0.1 mm. D, E) Tangential sections. Muscle fibres (arrows) around the oral siphon (os). ISH of BsMA2 (D) and BsTnT-c (E). Arrowheads: transverse fibres. Scale bar = 50 μm. F) Oral siphon: inner (arrows) and outer (arrowheads) systems of fibres (BsMA2). (tn) tentacle not stained. Scale bar = 50 μm. G) Tangential section of cloacal siphon (cs) of a system (BsMA2). Arrows: dorsal languets with muscle fibres (arrows). Scale bar = 0.15 mm. H) Fibre (arrow) in therecto-oesophageal trabecula (BsTnT-c). (int), intestine. Scale bar = 50 μm. I) Transverse section of unstriated muscle fibres (TEM). Muscle cellsare polarised. (mf), contractile elements; (ep), epidermis; (n), nucleus. Scale bar = 0.75 μm. J) Longitudinal section of an unstriated muscle fibre (mf). Arrowheads: dense bodies. Scale bar = 0.2 μm. K) Neuromuscular junction. Small vesicles (arrows) fill the nerve termination; arrowheads: dense material in the junctional space. In transverse section of an unstriated fibre (mf), no regular disposition of filaments is recognisable (inset; scale bar = 0.09 μm). Scale bar = 0.18 μm. L) Longitudinal section of myocardium. Sarcomeres are defined by arrows. Thin basal lamina (bl) faces the cardiac lumen (cl). (mf), myofibrils; (pc), pericardial cavity. Scale bar = 1 μm. M, N) Cardiac area (arrow). ISH of BsMA2 labels myocardium (M); no signal for BsTnT-c expression (N). (bs), branchial sac; (st), stomach. Scale bar = 50 μm.

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