Fig. 12

Schemes of innervation of the lophophore in different brachiopods, phoronids, and bryozoans. Structures that are thought to be homologous are marked by the same color. Among brachiopods, the inarticulate Lingula anatina has three brachial nerves: main, accessory, and lower. The accessory nerve is well developed and contributes to innervation of tentacles. All tentacles are innervated by four tentacular nerves: abfrontal, two laterofrontal, and frontal. The scheme is based on [10]. The rhynchonelliform Hemithiris psittacea has four brachial nerves: main, accessory, second accessory, and lower. The accessory brachial nerve is poorly developed and does not contribute to the innervation of tentacles, whereas the lower brachial nerve is stronger and more prominent than in L. anatina. In H. psittacea, the outer tentacles are innervated by six tentacular nerves: abfrontal, two lateroabfrontal, two laterofrontal, and frontal. The scheme is based on this report. The rhynchonelliform Gryphus vitreus has two brachial nerves: main and lower. The tentacles are innervated by the lower brachial nerve, which is well developed. Details of tentacle innervation are not known; the scheme is based on [17]. Among phoronids, juveniles have oval-shaped lophophore, three nerve elements of the lophophore: dorsal ganglion (dg), minor nerve ring (mnr), and tentacular main nerve ring (tnr), whereas adults have horseshoe-shaped lophophore and lack the minor nerve ring. In all phoronids, tentacles are innervated by six tentacular nerves: abfrontal, two lateroabfrontal, two laterofrontal, and frontal. Scheme of juvenile lophophore is based on [30]; scheme of adult lophophore is based on [31, 37]. Among bryozoans, ctenostome bryozoans have the cerebral ganglion (cg), circumoral nerve ring (con), and outer nerve ring (on), whereas many other bryozoans (i.e. phylactolaemates) lack the outer nerve ring. In bryozoans, tentacles are innervated by four tentacular nerves: abfrontal, two laterofrontal, and frontal. The scheme of ctenostome lophophore is based on [11]; the scheme of phylactolaemates is based on [33, 49]. Abbreviations: afn – abfrontal tentacular nerve; an – accessory brachial nerve; cg – cerebral ganglion; con – circumoral nerve ring; dg – dorsal ganglion; fn – frontal tentacular nerve; lafn – lateroabfrontal tentacular nerve; lfn – laterofrontal tentacular nerve; ln – lower brachial nerve; mn – main brachial nerve; mnr – minor nerve ring; pn – peritoneal neurite; sa – second accessory brachial nerve; tnr – tentacular main nerve ring