Fig. 3

Maximum intensity projections and volume rendering of f-actin staining scans of Hyalinella punctata. a: Lateral view of the lophophore and part of the tentacle sheath. Hyalinella possesses exclusively longitudinal musculature on the distal side of the tentacle sheath. Attachment sites of the retractor are visible at the lophophore and tentacle sheath. Also the abfrontal tentacle muscle band and the circular muscles of the pharynx is shown. b: Zooid viewed from the anal side surrounded by retractor muscles and body wall musculature. The retractors are attached to the animal at the tentacle sheath, ganglion, lophophore and at several spots at the digestive tract: pharynx, esophagus, cardia and caecum. The body wall possesses two muscular layers. c: The epistome musculature of Hyalinella from the proximal side. The muscle fibers are orientated laterally and are situated in the epistomal wall or traverse the coelomic cavity. d: Volume rendering of epistomal musculature in Hyalinella viewed from the proximal side. e: Distal ends of tentacles where strong f- actin positive signal in form of “knobs” in the epidermal layer of the tentacles is visible. f: Aperture musculature and the circular muscles located at the basal part of the tentacle sheath in H. punctata. The vestibular wall contains prominent circular as well as longitudinal musculature. The duplicature bands are attached to the tentacle sheath and body wall. The vestibulum dilatators traverse the coelomic cavity between vestibular wall and body wall. Abbreviations: a - anus, bwm - bodywall musculature, cae – caecum, db – duplicature bands, em - epistome musculature, ew – epistomal wall, int – intestine, o - orifice, phx - pharynx, rm. - retractor muscles, t – tentacle, tb – tentacle base, tm - tentacle musculature, ts – tentacle sheath, tsm - tentacle sheath musculature, tt – tentacle tips, vd – vestibulum dilatators, vwm – vestibular wall musculature