Abstract
Simple SummaryThe nervous system of Novocrania anomala adults is described for the first time. A table containing data on the lophophore innervation in species from three brachiopod subphyla is presented. A comparative analysis suggests a close relationship between the Craniiformea and the Rhynchonelliformea, and thereby supports the “Calciata” hypothesis of brachiopod phylogeny.Although the lophophore is regarded as the main synapomorphy of all lophophorates, the evolution of the lophophore in certain groups of lophophorates remains unclear. To date, the innervation of the lophophore has been studied with modern methods only for three brachiopod species belonging to two subphyla: Linguliformea and Rhynchonelliformea. In the third subphylum, the Craniiformea, there are data for juveniles but not for adults. In the current research, the innervation of the lophophore in Novocrania anomala adults was studied by immunocytochemistry and confocal laser scanning microscopy. In the spiral lophophore of adults of the craniiform N. anomala, each arm is innervated by six brachial nerves: main, additional main, accessory, second accessory, additional lower, and lower brachial nerves. Compared with other brachiopod species, this complex innervation of the lophophore correlates with the presence of many lophophoral muscles. The general anatomy of the lophophore nervous system and the peculiarities of the organization of the subenteric ganglion of the craniiform N. anomala have a lot in common with those of rhynchonelliforms but not with those of linguliforms. These findings are consistent with the “Calciata” hypothesis of the brachiopod phylogeny and are inconsistent with the inference that the Craniiformea and Linguliformea are closely related.
Highlights
Brachiopods are benthic marine animals that form a phylum consisting of 400 recent species and more than 10,000 extinct species
Parts of the Biology 2022, 11, 406 lophophores were fixed for semi-thin sectioning, scanning electron microscopy (SEM), and immunocytochemistry combined with confocal laser scanning microscopy (CLSM)
The lophophore nervous system of brachiopods has been mostly studied by histological methods [29,30,33,34], and only a few species have been investigated by electron microscopy, immunocytochemistry, and confocal laser scanning microscopy [15,19,27,28,35–37]
Summary
Brachiopods are benthic marine animals that form a phylum consisting of 400 recent species and more than 10,000 extinct species. The first two subphyla are traditionally gathered into “inarticulate” brachiopods, because their shell valves lack articulate structures. The clade of “inarticulate” brachiopods includes phoronids, which are the closest relatives of brachiopods; phoronids are regarded as “brachiopods without shell” [4] This close relationship is supported by many molecular data, and the clade, which includes brachiopods and phoronids, is called Brachiozoa [5–7]. The shell valves of brachiopods in the subphylum Rhynchonelliformea have articulate structures and are traditionally regarded as “articulate” brachiopods. A pelagic juvenile presents in the life cycle, whereas craniiformes lack such a juvenile and have bilobed lecitotrophic larvae [10,11]. Such larvae are supposed to form most of the fossil brachiopods [12]. According to “Calciata hypothesis”, craniiforms and rhynchonelliforms with calcic shell are close relatives
Sign-in/Register to view highlights & summary 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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
