Fig. 4

Maximum intensity projections and volume renderings of f-actin stainings of the apertural region and body wall in Cristatella and Pectinatella. a: The musculature of the aperture region in Cristatella. The apertural musculature consists of several muscle sets: the duplicature bands which are located between the body wall and tentacle sheath and vestibulum dilatators which are located between the body wall and vestibular wall, which also contains musculature. Between the vestibular wall and tentacle sheath the diaphragm sphincter is situated. b: Apertural region in Pectinatella. Note that parts of the body wall musculature are removed. The circular arrangement of the duplicature bands and vestibulum dilatators are visible around the vestibular wall and tentacle sheath. c and d: In Pectinatella magnifica a third muscular layer in the body wall exists in some areas. This muscle layer is arranged diagonally to the other two. e: Two layers of body wall musculature form the regular muscular mesh in Cristatella mucedo. Abbreviations: bwm – body wall musculature, db - duplicature bands, dsph -diaphragmatic sphincter, ep - epidermis, o - orifice, os - orifice sphincter, s – septa, ts - tentacle sheath, vd - vestibulum dilatators, vw - vestibular wall, vwm - vestibular wall musculature