Fig. 10

Musculature of the lophophore of Hypophorella expansa. F-actin staining (glow), acetylated alpha tubulin (green). CLSM. a Lateral view of the lophophoral base and foregut. Volume rendering. b Schematic drawing of the main muscular parts of the lophophoral base. c Optical section showing diagonal tentacle sheath muscles and abfrontal lophophoral base muscles. Note also the distinct striation of some retractor muscle fibres. d Optical section through the foregut showing the myoepithelium of the pharynx. e Lateral view of longitudinal tentacle muscle bands showing the more distally located start of the frontal muscle bands. Volume rendering. f Close-up of tentacle tips showing distinct circular, sphincter-like muscles (arrows). Maximum intensity projection. g Close-up of lophophoral base muscles. Lateral view. Volume rendering. Note the striation of buccal dilatators and the mixed, smooth and striated, forms of retractor muscle fibres. Abbreviations: afm – abfrontal lophophoral base muscles, afr – abfrontal neurite bundle, bd – buccal dilatators, btm – basal tranversal muscle, c – cilia, ccm – caecal muscles, ftm – frontal tentacle muscles, lb. – lophophoral base, mo – mouth opening, ph – pharynx, pmy – pharyngeal myoepithelium, pxm – pharyngeal ring muscles, rm. – retractor muscles, smr – smooth retractor muscle fibres, str – striated retractor muscle fibres, t – tentacle, tm – tentacle muscles (abfrontal), tsm – tentacle sheath muscles, vm ‘v’-shaped lophophoral base muscles