Abstract
Evolutionary relationships among members of the Lophophorata remain unclear. Traditionally, the Lophophorata included three phyla: Brachiopoda, Bryozoa or Ectoprocta, and Phoronida. All species in these phyla have a lophophore, which is regarded as a homologous structure of the lophophorates. Because the organization of the nervous system has been traditionally used to establish relationships among groups of animals, information on the organization of the nervous system in the lophophore of phoronids, brachiopods, and bryozoans may help clarify relationships among the lophophorates. In the current study, the innervation of the lophophore of the inarticulate brachiopod Lingula anatina is investigated by modern methods. The lophophore of L. anatina contains three brachial nerves: the main, accessory, and lower brachial nerves. The main brachial nerve is located at the base of the dorsal side of the brachial fold and gives rise to the cross neurite bundles, which pass through the connective tissue and connect the main and accessory brachial nerves. Nerves emanating from the accessory brachial nerve account for most of the tentacle innervation and comprise the frontal, latero-frontal, and latero-abfrontal neurite bundles. The lower brachial nerve gives rise to the abfrontal neurite bundles of the outer tentacles. Comparative analysis revealed the presence of many similar features in the organization of the lophophore nervous system in phoronids, brachiopods, and bryozoans. The main brachial nerve of L. anatina is similar to the dorsal ganglion of phoronids and the cerebral ganglion of bryozoans. The accessory brachial nerve of L. anatina is similar to the minor nerve ring of phoronids and the circumoral nerve ring of bryozoans. All lophophorates have intertentacular neurite bundles, which innervate adjacent tentacles. The presence of similar nerve elements in the lophophore of phoronids, brachiopods, and bryozoans supports the homology of the lophophore and the monophyly of the lophophorates.
Highlights
Members of the phylum Brachiopoda are marine invertebrates with a unique body plan
L. anatina has a shell, which consists of two valves, and a long muscular peduncle that is fastened to the substratum (Fig 1A)
Lophophore morphology is rather similar among all three phyla of the lophophorates
Summary
Members of the phylum Brachiopoda are marine invertebrates with a unique body plan. Adult brachiopods are benthic animals, and most are attached to the hard substratum. Adults of the brachiopod Lingula anatina (Lamark, 1801) are confined to brackish intertidal habitats, where they live in burrows in the sand. Like adults of other brachiopods, L. anatina adults are suspension feeders that extract food from the surrounding water using a structure known as the lophophore. The lophophore performs several main functions including the collecting of food particles, the brooding of embryos, and respiration. Lophophores are known in some other bilaterians–the phoronids and bryozoans. Food-collecting and waste-rejecting mechanisms in Glottidia pyramidata and the persistance of lingulacean brachiopods in the fossil record.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
