Serotonin-like immunoreactive nerve elements of the lophophore of Phoronis ovalis. Z-projections (A,B) and 3D-reconstructions (C-E) after mono- and double staining for 5-HT (serotonin) (green), acetylated α-tubulin (grey), and phalloidin (blue). (A) general view of serotonin-like immunoreactive nerve net developed in the anterior portion of the body and the lophophore, (B) main nerve elements viewed from the anal side, (C) reconstruction of inner nerve centre with inner nerve ring and dorsal ganglion with tentacular nerve ring, (D) inner nerve ring viewed from the left. The left side of the lophophore is deleted, (E) connection between inner ganglion and dorsal ganglion viewed from the left. Abbreviations: 5ht-p, serotonin-like immunoreactive perikarya connected with the inner nerve ring; afn, abfrontal neurite bundle; dg, dorsal ganglion; ig, inner ganglion; inr, inner nerve ring; lph, lophophore; t, tentacle; tnr, tentacular nerve ring.