Fig. 6

Some details of the cerebral ganglion and visceral nerve organization in Amathia gracilis. Z-projections (a–f) of the lophophore after mono-, double, and triple staining for tyrosinated α-tubulin (green), 5-HT (serotonin) (white), and DAPI (magenta). a Anal view of the cerebral ganglion. Three commissures are indicated by asterisks. b Anal view of the central zone of the cerebral ganglion, which consists of upper and lower parts. c Serotonin-like immunoreactive nerve elements within the lophophore. Lateral view; the oral side is to the left, and the anal side is to the right. d Serotonin-like immunoreactive perikarya located at the base of the lophophore between tentacle bases. e Some details of the ganglion organization: ganglion ventro-lateral nerves are associated with large multipolar perikarya. Lateral view. f Medial visceral nerve starting from the cerebral ganglion. g 3D reconstruction of the serotonin-like innunoreactive parts of the cerebral ganglion and the circum-oral nerve ring including the intertentacular neurite bundles. h Volume rendering of the serotonin-like immunoreactive nervous system. The anal side is to the right; the oral side is to the left. Numbers 1-8 indicate serotonin-like immunoreactive perikarya. Large arrows indicate the “gaps” between two analmost and six oralmost perikarya. Abbreviations: ci - cilia of tentacles; cg - cerebral ganglion; cgb - proximal part of the cerebral ganglion; cgn - ventro-lateral nerves of the cerebral ganglion; con - circum-oral nerve ring; hpk - perikaryon of the cerebral ganglion ventro-lateral nerve; ldl - lophophoral dorso-lateral nerves; lpg - lower portion of the cerebral ganglion; mf - medio-frontal nerve of tentacle; mvn - medial visceral nerve; phr - pharynx; sc - serotonincilia; sn - serotonin-like immunoreactive intertentacular neurites; spk - serotonin-like immunoreactive perikarya between tentacles; t - tentacle; upg - upper portion of the cerebral ganglion