Fig. 5

Overview of the musculature in the digestive tract and the funiculus shown in maximum intensity projections and volume renderings of f- actin staining in Cristatella and Pectinatella. a: Overview of the muscular system in a young Pectinatella colony shortly after germinating. Two zooids are visible, one is completely protruded. The tentacle crown bears all tentacles. Prominent retractor muscles are visible and the aggregation of ring musculature at the orifice forms the orifice sphincter. The body wall contains prominent musculature. b: Oral view of Cristatella and lateral view on a lophophoral arm where the intertentacular membrane is visible. Lophophoral arm musculature branches off to the tentacles. The tentacle sheath contains longitudinal and circular musculature, note the detail in the lower left corner of the tentacle sheath musculature. The u-shaped digestive tract contains circular musculature. c: Lateral view of the digestive tract of Pectinatella. Denser aggregation of the musculature at the caecum is visible. d: Lateral view of the digestive tract in Cristatella. At the beginning of the digestive tract, at the proximal end of the caecum and at the rectum a denser aggregation of musculature is visible. e: Detail of funiculus musculature and retractor muscles in Cristatella. Both contain smooth muscle fibers and insert at the basal part of the body wall, in case of Cristatella at the creeping sole. f: Detail of the funiculus in Pectinatella where the fine longitudinal muscles are visible. Abbreviations: bwm – body wall musculature, ca - cardia, cae - caecum, csm - creeping sole musculature, dtm - digestive tract musculature, es - esophagus, ep - epidermis, fm - funiculus musculature, int - intestine, lam - lophophoral arms musculature, os - orifice sphincter, ph - pharynx, rm. - retractor muscle, t - tentacles, ts -tentacle sheath, tsm - tentacle sheath musculature, tt - tentacle tips