Fig. 2

Histological details and 3D-reconstruction of the distal area of Asajirella gelatinosa. A–C Oblique sections showing the vestibulum as invagination with circular muscles adjacent to the diaphragmatic sphincter muscle (A). The latter separates the vestibulum from the atrium (B) and continues into the tentacle sheath (C). Vestibulum dilatators are present in the distal area and connect the body wall to the vestibulum. In addition, numerous coelomocytes are present (A, arrow). D, E Details of the duplicature bands show the longitudinal muscles of the body wall project into the tentacle sheath (arrow) via the duplicature band connected to the tentacle sheath. F 3D-reconstruction of the apertural area shows the general anatomy of the latter. the vestibular wall is followed by the tentacle sheath. The duplicature bands are arranged in a circular plain around the tentacle sheath. at atrium, bw body wall, bwm body wall musculature, cc coelomic cavity, db duplicature bands, dis diaphragmatic sphincter, ed epidermis, l lophophore, o orifice, ooc oocytes, p peritoneum, ts tentacle sheath, tsm tentacle sheath musculature, vd vestibulum dilatators, v vestibulum, vm vestibular muscles, vw vestibular wall