Fig. 22

Syllinae. Parapodial innervation. Maximum intensity z-projection of ventral sections. a1: α-tubulin-lir (grey) of a parapodium of Plakosyllis brevipes. Three neurite bundles leave the ventral nerve cord and innervate the parapodium. A cluster of somata (green dotted line) is innervated by a small neurite bundle coming from root 1 of the main parapodial neurite bundle. The main parapodial neurite bundle and the third segmental ring neurite bundle are connected (yellow arrowhead). a2: Serotonin-lir (orange) and cell nuclei (magenta) of the same parapodium of P. brevipes as in A1. The serotonin-lir signal is not as defined as the α-tubulin-lir but nearly all neurite bundles of the parapodial innervation are stained. Only the signal of the innervation of the ventral cirrus appears much weaker. b1: α-tubulin-lir (grey) of a parapodium of Syllis tyrrhena. Four neurite bundles form the parapodial innervation. b2: Serotonin-lir (orange) and cell nuclei (magenta) of the same parapodium of S. tyrrhena as in B1. The signal of the parapodial neurite bundles is restricted to the most anterior and the main neurite bundle. (C1 and C2 are the same as in B1 and B2 in Fig. 19, but are shown here again for a better overview.) c1: α-tubulin-lir (grey) of a parapodium of Syllis garciai. Five neurite bundles form the parapodial innervation. c2: Serotonin-lir (orange) and cell nuclei (magenta) of the same parapodium of S. garciai as in C1. The parapodial innervation is hardly stained. Staining results of serotonin-lir differed greatly among individuals. Scale bars = 50 μm. Abbreviations: acn – neurite bundle accompanying the acicle; ap – anterior neurite bundle entering the parapodium; cn – neurite bundle accompanying chaetae; cr – ciliary receptor; dc – dorsal cirrus; dpc – neurite bundles forming distal dorsal parapodial connective; lln – lateral longitudinal neurite bundle; mn – median ventral nerve; mp – main parapodial neurite bundle entering parapodium; mvn – main ventral nerve; n - nephridium; pln – neurite bundles innervating parapodial lobe; pmn – paramedian ventral neurite bundle; rp1- root 1 of main parapodial neurite bundle; rp2 – root 2 of main parapodial neurite bundle; scs – segmental cluster of somata on segmental neurite bundle III; vcn – neurite bundle innervating ventral cirrus; vgl – ganglion of ventral nerve cord; vln – ventral longitudinal neurite bundle; vnc – ventral nerve cord. Segmental neurite bundles in yellow: 1 – first fine segmental neurite bundle; I-IV – segmental neurite bundles forming ring commissures, II refers to all neurite bundles comprising the parapodial innervation