Fig. 8. The first monoaminergic neurones in trochophores of Helisoma and Lymnaea at stage 19 (20%). (A,C-F) Anti-tubulin Immunostaining (red). (A) Helisoma; anti-5-HT immunolabelling (green). Anterior sensory neurones (arrows) are located on both sides of the mouth (m), and project to the pedal ciliary band (pb); pn, cilia in protonephridia (LSM projection, 48x0.6 µm). (B) Lymnaea; glyoxylic acid-induced fluorescence of catecholamines; conventional epifluorescence. The pair of the first anterior cells (arrows) is located above the mouth (m). (C) Lymnaea; anti-tyrosine hydroxylase immunolabelling (green). Anterior neurones (arrows) make a varicose network underneath the apical ciliary plate (LSM projection, 26x1 µm). (D) Lymnaea; anti-5-HT immunolabelling (green). High power image of the anterior neurone with a short thick ciliated apical fibre, thin basal fibre and two short lateral fibres (arrows) emanating from the soma (LSM projection, 54x0.35 µm). (E) Helisoma; anti-5-HT immunolabelling (green). The anterior neurone also has a thick ciliated apical fibre, a thin basal fibre and two short lateral fibres (arrows) (LSM projection, 43x0.3 µm). (F) Helisoma; anti-5-HT immunolabelling (green). Varicose network made by the fibres of the anterior neurones underneath the pedal ciliary band (pb) (LSM projection, 26x0.4 µm). Scale bars: 20 µm in A,B; 10 µm in C-F.