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Fig. 1 | BMC Evolutionary Biology

Fig. 1

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. 1

Schematic representation of the distribution of serotonin-lir perikarya in (a & b) the Gymnolaemata and (c & d) the Phylactolaemata. As shown in the current study the oral side of the Gymnolaemata always contains three serotonin-lir perikarya (turquoise) followed by a ‘serotonergic gap’ and the remaining lateral and anally situated tentacles (blue). Preliminary data on the Phylactolaemata hint to a similar arrangement of oral tentacles (turquoise), a kind of gap, followed by lateral tentacles rising up to the lophophore arms (blue). The inner lophophoral concavity shows no serotonin-lir perikarya. Consequently, it is possible that the inner row of tentacles (orange) represents an apomorphic feature of the Phylactolaemata. b is the cheilostome gymnolaemate Electra posidonia. d is the phylactolaemate Pectinatella magnifica. Abbreviations: cg – cerebral ganglion, loc – lophophoral concavity, mo – mouth opening

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