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Fig. 2 | BMC Evolutionary Biology

Fig. 2

From: The serotonin-lir nervous system of the Bryozoa (Lophotrochozoa): a general pattern in the Gymnolaemata and implications for lophophore evolution of the phylum

Fig. 2

The general structure of the serotonin-lir nervous system in selected Gymnolaemata based on confocal laserscanning microscopy scans. a-c Serotonin-lir nervous system in the cheilostome Membranipora membranacea. a Volume rendering of the serotonin-lir nervous system (yellow) with nuclei (blue). View slightly oblique from the lateral side. The arrow points to the ‘serotonergic gap’ where the tentacle base does not possess a serotonin-lir perikaryon. b Optical section of the same specimen as in (a) showing the serotonin-like immunoreactivity in the cerebral ganglion. c Optical section of the same specimen as in (a) showing the series of serotonin-lir perikarya in the intertentacular pits including the ‘serotonergic gap’ (arrow). d Volume rendering of the serotonin-lir nervous system in the cheilostome Cryptosula pallasiana. The arrows point to the ‘serotonergic gap’. Asterisks mark the three oral serotonin-lir perikarya. e Volume rendering of the serotonin-lir nervous system in the cheilostome Electra pilosa. The arrows point to the ‘serotonergic gap’. Asterisks mark the three oral serotonin-lir perikarya. f Volume rendering of the serotonin-lir nervous system in the ctenostome Amathia semiconvoluta. This species has only 8 tentacles and consequently only 6 distinct serotonin-lir perikarya at the lophophoral base. The arrows point to the ‘serotonergic gap’. Asterisks mark the three oral serotonin-lir perikarya. Abbreviations: cg – cerebral ganglion, con – circum-oral nerve ring , itp – intertentacular pits, lb – lophophore base, mo – mouth opening, ph – pharynx, sc – serotonin-lir cilium(?), sp – serotonin-lir perikarya, t – tentacle

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