Fig. 24

Syllis tyrrhena. Parapodial innervation of stolons. a1, a2: Maximum-intensity z-projections of dorsal sections. a1: Serotonin-lir. The dorsal side of the segment is innervated by an epidermal plexus emerging from root 2 of the parapodial innervation. a2: α-tubulin-lir. Similar to serotonin-lir staining, some of the neurite bundles forming the epidermal less are less prominent. a3: Volume rendering of the parapodium, dorsolateral view. α-tubulin-lir (grey), serotonin-lir (orange). α-tubulin-lir neurite bundles innervating the notopodial swimming chaeta are segmented in green, serotonin-lir signal accompanying the notopodial chaeta are segmented in red. All four dorsal connectives of the parapodium are visible. Yellow arrow: fourth dorsal commissure present only in parapodia of stolons of S. tyrrhena. b1, b2: Maximum-intensity z-projections of ventral sections. b1: Serotonin-lir. The nephridium is accompanied by a strong serotonin-lir signal. A neurite bundle (green arrowheads) connects the anterior parapodial neurite bundle to segmental neurite bundle I and is only found in the stolons. b2: α-tubulin-lir showing the course of the second segmental nerve towards the parapodium. b3: Volume rendering of the parapodium, ventral view. α-tubulin-lir (grey), serotonin-lir (orange). α-tubulin-lir neurite bundles innervating the notopodial swimming chaeta are segmented in green, serotonin-lir signal accompanying the notopodial chaeta are segmented in red. c: Schema of the parapodium of the stolon. The innervation is essentially the same as in the stock animals but for a few additions; an additional dorsal connective (yellow arrow) forms from the median parapodial connective, enveloping the notopodial chaetae. The chaetae are innervated by fine α-tubulin-lir fibres and a strong serotonin-lir signal surrounds the notopodial chaeta. A neurite bundle connects the anterior parapodial neurite bundle to segmental ring neurite bundle I. Scale bars = 50 μm. Abbreviations: ap – anterior neurite bundle entering the parapodium; acn – neurite bundle inaccompanying acicle; cn – neurite bundle accompanying chaetae; dcn – neurite bundle innervating dorsal cirrus; dep – dorsal epidermal plexus; dln – dorsal longitudinal neurite bundle; dlp – distal innervation of the parapodial lobe; dpc – distal dorsal parapodial connective; lln – lateral longitudinal neurite bundle; mn – median ventral nerve; mpc – median dorsal parapodial connective; mvn – main ventral nerve; n – nephridium; nc – notochaetae; ncn – α-tubulin-lir neurite bundle innervating notochaetae; nsc – serotonin-lir signal accompanying notochaetae; pin – nervous plexus innervating intestine; pln – neurite bundles innervating parapodial lobe; prc – proximal dorsal parapodial connective; rp1 – root 1 of main parapodial neurite bundle; rp2 – root 2 of main parapodial neurite bundle; vcn – neurite bundle innervating ventral cirrus; vgl – ganglion of ventral nerve cord; vln – ventral longitudinal neurite bundle. Segmental neurite bundles in yellow: I – first segmental ring neurite bundle; II.I-II.V – neurite bundles comprising parapodial innervation; llr - dorsal commissure of root 2 of II