Fig. 5

Histological details of the lophophoral base of Asajirella gelatinosa. A, B Cross section through the lophophore base above the cerebral ganglion of a protruded (A) and retracted (B) zooid. The epistomial horns bear a large lumen. The epistome coelom ascends via a canal between the epistomial horns. C Longitudinal section through the lophophore base of a protruded zooid. Centrally, the epistome coelom extends to a large cavity. Proximally the latter is flanked by projections of the cerebral ganglion and the ring canal, whereas the ciliated forked canal ascends distally. D–E Detailed cross sections through the epistome and lophophoral concavity at different heights. Distally, the coelom (forked canal) of three tentacles in the lophophoral concavity are connected (D), whereas they are separate more proximally (E, F). In addition, the epistome includes a muscle basket in its lining and muscles traversing the epistome coelom. bw body wall, cc coelomic cavity, clc coelomocytes, ec epistome coelom eh epistomial horns, emb epistome muscle basket, emt traversing muscles of the epistome, ep epistome, fc forked canal, gl ganglion lumen, gh ganglionic horns, itm intertentacular membrane, la lophophoral arm, loc lophophoral concavity, mo mouth opening, nb neurite bundle, ph pharynx, rc ring canal, t tentacle, tc tentacle coelom, ts tentacle sheath, asterisk lumen of the epistomial horn