Fig. 5. Confocal imaging of neuroepithelial cells (NECs) and associated innervation of the gill filaments and lamellae in zebrafish. NECs were labelled with antibodies against 5-hydroxytryptamine (5-HT; green) and SV2 (red in A; red or yellow in B), and nerve fibres were identified by zn-12 immunoreactivity (red). (A) SV2-positive NECs (arrows) were found in the filament (F) and received innervation from intrinsic nerve fibres (iNF) and a plexus of extrinsic nerve fibres (eNF). Extrinsic nerve fibres were also found in the lamellae (L). Scale bar, 20 µm. (B) Dual exposure image in A showing, in addition, 5-HT-positive immunofluorescence (green) and that some NECs containing SV2 are also serotonergic.