Fig. 3

Prosphaerosyllis marmarae. Innervation of prostomium and anterior segments a-c: Single optical frontal sections of the same individual. Anterior end and first two chaetigers, slightly oblique. α-tubulin-lir (grey), cell nuclei (magenta) and f-actin (orange glow) staining combined. a: Dorsal; white arrow marks neurite bundle reaching from drcc into posteroventral (possible nuchal) cluster of somata (pink dotted line). Cell nuclei within nuchal lobes (green line) are hard to recognise. The somata of the brain (red line) form a pair of dorsal lobes. b: Median portion of the brain. Fibres from the tentacular cirrus neurite bundle enter the first of the tentacular clusters of somata (red dotted line) c: Ventral section of the brain. Arrow indicates neurite bundles reaching into the posterior inferior cluster of somata (pink dotted line), next to the nuchal neurite bundle. Second tentacular cluster of somata (black dotted line) receives fibres from the tentacular cirri neurite bundle. d: Dorsal maximum intensity z-projection of anterior end and first three chaetigers, α-tubulin-lir (white) and cell nuclei (magenta). Yellow arrow indicates loop where stomatogastric neurite bundles enter pharyngeal epithelium. e-j: Maximum intensity z-projections of different sections of one individual. e: Dorsal part of the brain (α-tubulin-lir). f: Ventral part of the brain. Black arrowhead indicates the neurite bundle giving rise to ventral, lateral and dorsal longitudinal neurite bundles. g: Serotonin-lir of the brain, dorsal. A third stomatogastric ring neurite bundle is visible. h: Serotonin-lir of the brain, ventral. i: Median planes of α-tubulin-lir and cell nuclei. Posterior inferior clusters of somata (dotted pink lines) receive fibres from drcc (white arrow) and nuchal neurite bundle (black arrow). j: Colour-coded z-projection of ventro-median planes of the same individual as in E-I to visualise individual stomatogastric neurite bundles. A strong stomatogastric neurite bundle extends towards the lips (white arrowhead). Scale bars = 50 μm. Abbreviations: ae – anterior eye; br – brain; cc – circumoesophageal connective; cno – cilia of support cells of nuchal organ; cvr – commissure of vrcc; dc – dorsal cirrus; dl – dorsal lobe of the brain; dlm – dorsal longitudinal muscle; dln – dorsal longitudinal neurite bundle; drcc – dorsal root of circumoesophageal connective; es – eyespot; la – lateral antenna; lfs – laterofrontal sense organ; llm – lateral longitudinal muscle; lln – lateral longitudinal neurite bundle; man – neurite bundles innervating median antenna; mlp – muscular layer of pharynx; nn – nuchal neurite bundle; pa – palp; pam – palp muscle; pe – posterior eye; ph – pharynx; pk – serotonin-lir perikarya; plg – parapodial ganglion/cluster of somata; pn1 – main palp neurite bundle; pn2 – palp neurite bundle originating from drcc; pon – posterior neurite bundle of the brain; ppl1 – parapodial lobe of first chaetiger; sc – sensory cells; sn – segmental neurite bundle; sn1 and 2 – segmental neurite bundles of tentacular segment; sp. – sensory papillae; sr – serotonin-lir stomatogastric ring neurite bundle; stgn 1–5 – stomatogastric neurite bundles 1–5; tcn – neurite bundle innervating tentacular cirri; th – tooth; vlm – ventra longitudinal muscle; vnc – ventral nerve cord; vrcc – ventral root of circumoesophageal connective