Fig. 11

Evolution of nervous system and homology of segments and body regions in Siboglinidae. Consensus phylogenetic tree constructed from a combination of recent molecular phylogenies: clade of Osedax spp. resolved based on [29], Vestimentifera - [27], Frenulata - [1, 16], interrelationship of these clades - [27], serpulid outgroups - [13, 18, 19]. Neural characters provided in Table 1 are traced on the tree showing the 10 unambiguous character transformations on the main branches (only apomorphic states shown; for plesiomorphic states see Table 1). a-i Schemes of the main ventral cords and brains in Siboglinidae. Green color indicate fused prostomial + peristomial region; pink and yellow colors indicate following body segments of suggested homology among siboglinids and the metatrochophore of Pomatoceros lamarckii. Nerves and perikarya are drawn in red; ciliary bands in grey. Sidebars indicate body regions according to traditional siboglinid terminology. a Metatrochophore of P. lamarckii (Serpulidae)[61]. b Metatrochophore of Siboglinum poseidoni (Frenulata) [68]. c Combination of adult Siboglinum caulleryi (most of the body [64]) and S. fiordicum (opisthosoma)(Frenulata)[53]. d Adult Nereilinum murmanicum (Frenulata)[55]. e Adult Sclerolinum contortum [26]. f Juvenile Riftia pachyptila (Vestimentifera)[45]. g Female Osedax priapus. h Female O. mucofloris. i. Dwarf male of O. rubiplumus [12]. Abbreviations: at – apical tuft, i – brain, i – broadened ventral cord, cc – circumesophageal connectives, cb – ciliary band, ch – chaetae, cvc –commissure of vc, cvn – crossing neurites of vc, mn – median nerve, mvn - median ventral nerve, og – opisthosomal ganglion, pcr – telotroch, pg – posterior ganglion, pgn – posterior ganglion nerve, pha – phaosome, phr – photoreceptor, pn – palp nerve, pr – prototroch, pac – perikarya of cvc, rco – prototroch ring commissure, rn – ring nerve, ron – ring ovisac nerve, rtn – posterior trunk ring nerve, sbg – subesophageal ganglion, smap – serotonergic perikarya of vc, tco – terminal commissure, tn – palp nerve, tg – trunk ganglion, vc – ventral cord, vcf – ventral ciliary field, vp – ventral plexus between vc