Fig 4 - uploaded by Thomas Schwaha
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Fenestrulina joannae. A Overview of a zooid. B Overview from the frontal side, showing alpha-tubulin-lir in orange and f-actin in gray. Volume rendering. C Overview from the frontal side, showing alpha-tubulin-lir structures in orange. Volume rendering. D Detail of the lophophoral base. Alphatubulin-lir in orange. Volume rendering. E Detail of apertural area. Alpha-tubulin-lir in gray. Maximum intensity projection. Abbreviations: afn -abfrontal tentacle neurite bundle, cg -cerebral ganglion, CON -circumoral nerve ring, ctsn -compound tentacle sheath nerve, d -distal, dtsn -direct tentacle sheath nerve, int -intestine, lb. -lophophoral base, lvn -laterovisceral neurite bundle, mvn -mediovisceral neurite bundle, opn -opercular nerve, opo -operculum occlusor, p -proximal, pbs -parietal branching site, pdi -parietodiaphragmatic muscle, pdin -parietodiaphragmatic nerve, phmpharyngeal musculature, php -pharyngeal nerve plexus, pm -parietal muscle, pmn -parietal muscle nerve, rm. -retractor muscle, sph -sphincter muscle, spn -sphincter nerve, tc -tentacle cilia, tfd -trifid neurite bundle, tm -tentacle muscle
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Background
Bryozoans are sessile aquatic suspension feeders in mainly marine, but also freshwater habitats. Most species belong to the marine and calcified Cheilostomata. Since this taxon remains mostly unstudied regarding its neuroanatomy, the focus of this study is on the characterization and ground pattern reconstruction of the autozooidal nerv...
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Context 1
... nerve plexus, pm -parietal muscle, pmn -parietal muscle nerve, rm. -retractor muscle, sph -sphincter muscle, spn -sphincter nerve, tc -tentacle cilia, tfd -trifid neurite bundle, tm -tentacle muscle, white arrows indicate the position of duplicature bands morphology of E. posidoniae is similar to conditions exhibited in Fenestrulina joannae ( Fig. 4B) and Myriapora truncata (Fig. 5B). Bugula neritina lacks an operculum occlusor (Fig. 6B) and the visceral plexus is absent in Collarina balzaci (Fig. 7B). In contrast, Chorizopora brongniartii has a prominent muscular plexus around the digestive tract (Fig. ...
Citations
... In the past decade, several studies were conducted on gymnolaemate bryozoans using immunocytochemical and confocal laser scanning microscopical methods (e.g., Decker et al., 2020;Prömer et al., 2021;Pröts et al., 2019;Schwaha & Wanninger, 2015;Schwaha et al., 2011;Temereva & Kosevich, 2016;Weber et al., 2014). The results are in accordance with previous descriptions of tubulinergic F I G U R E 17 Sundanella sibogae. ...
... 3D, three-dimensional; cg, cerebral ganglion; con, circum-oral nerve ring; dtn, direct tentacle sheath nerve; ito, intertentacular organ; lb, lophophoral base; lex, lateral peritoneal extension. The highest resemblance of the sundanellid nervous system is with those of other gymnolaemates with high tentacle numbers as, for example, in pherusellids (Decker et al., 2020) or the cheilostome Myriapora truncata (Prömer et al., 2021). In general, there seems to be no distinct deviation from the general structure of the nervous system, except that no laterofrontal neurite bundles could be verified in the current study. ...
Ctenostome bryozoans are a small group of gymnolaemates that comprise only few hundred described species. Soft-tissue morphology remains the most important source for analyzing morphological characters and inferring relationships within this clade. The current study focuses on the genus Sundanella, for which morphological data is scarce to almost absent. We studied two species of the genus, including one new to science, using histology and 3D-reconstruction techniques, and confocal laser scanning microscopy. Sundanella generally has a thick, sometimes arborescent cuticle and multiporous interzooidal pore-plates. The lophophore is bilateral with an oral rejection tract and generally has 30 or 31 tentacles in both species. The digestive tract shows a large cardia in S. floridensis sp. nov. and an extremely elongated intestine in S. sibogae. Both terminate via a vestibular anus. Only a single pair of parieto-diaphragmatic muscles is present and 4-6 duplicature bands. Both species show a large broad frontal duplicature band further splitting into four individual bands. The collar is vestibular. Sundanella sibogae shows highly vacuolated cells at the diaphragm, whereas S. floridensis sp. nov. has unique glandular pouches at the diaphragmal area of the tentacle sheath. Such apertural glands have never been encountered in other ctenostomes. Both species of Sundanella are brooders that brood embryos either in the vestibular or cystid wall. Taken together, the current analysis shows numerous characters that refutes an assignment of Sundanella to victorellid ctenostomes, which only show superficial resemblance, but differ substantially in most of their soft-body morphological traits. Instead, a close relationship with other multiporate ctenostomes is evident and the families Pherusellidae, Flustrellidrae and Sundanellidae should be summarized as clade 'Multiporata' in the future. This article is protected by copyright. All rights reserved.
... atc, "apodemal" tendon cell; atp, projection of "apodemal" tendon cell; bt, bundle of thick filaments; cav, body cavity of the avicularium; cmd, body cavity of the mandible; cur, cuticular ridge; ec, ectocyst; fl, layers of thick fibrils; fm, frontal membrane; ls, longitudinal swellings; mad, mandible adductors; mmab, median mandible abductor; oiol, outgrowth of the inner organic layer; p, palate; pmw, proximal mandible wall; rl, rudimentary lophophore; umw, upper mandible wall; uvm, upper vestibular membrane neurites forming an elaborate network in the neuropile of the cerebral ganglion. The absence of 5HT-positive cells in the cerebral ganglion of the avicularium is not surprising: similar feature was reported for the cerebral ganglion of autozooids in several gymnolaemates(Prömer et al., 2021;Schwaha et al., 2011;Schwaha & Wanninger, 2015;Temereva & Kosevich, 2016). As for the receptor cells of the frontal membrane, their sensory part is dendritic and embedded in the inner organic layer of the ectocyst. ...
... As for the receptor cells of the frontal membrane, their sensory part is dendritic and embedded in the inner organic layer of the ectocyst. This is a highly modified state compared with other bipolar 5HT-positive receptor cells reported for the autozooids of gymnolaemates: such cells are located between the tentacle bases and usually have a short peripheral projection equipped with a cilium(Prömer et al., 2021;Schwaha et al., 2011;Schwaha & Wanninger, 2015;Temereva & Kosevich, 2016). Based on our data on the location and ultrastructure of the sensory cells of the frontal membrane, we can assume that their possible function is to register changes in the shape of the frontal membrane. ...
Bryozoans are small benthic suspension-feeding colonial animals. Among this phylum, there are representatives showing a lesser or greater degree of polymorphism, and the most common type of polymorphic zooids is the avicularium. Here we present a detailed description of the bird's-head shaped avicularium in Dendrobeania fruticosa. The body cavity of the avicularium demonstrates an acoelomate condition: along the cystid walls, there is neither the layer of extracellular matrix towards the epidermis, nor coelomic lining. However, a layer of an extracellular matrix and epithelialized cells lie under the epidermis of the tentacle sheath. Probably, such construction helps the tentacle sheath to acquire some rigidity – it is the only region of the body wall without an ectocyst. We did not find typical funicular strands in the avicularium, but there is a delicate mesh composed of stellate cells with thin and long projections, which sometimes isolate the spaces filled with a heterogeneous matrix. The proximal ends of the adductors, abductors, and polypide retractors are attached to the body wall via typical epidermal tendon cells, which possess numerous bundles of tonofilaments. The distal ends of the abductors and adductors attach to the frontal membrane or upper vestibular membrane, respectively. The inner organic layer of the ectocyst in these regions forms large protrusions, from which numerous thin outgrowths branch off. We suggest them to be a functional analogue of apodemes and apodemal filaments in arthropods. “Apodemal” tendon cells have long and thin projections that line the outgrowths of the ectocyst and surround the distal ends of the muscle cells. At these sites, “apodemal” tendon cells possess numerous tonofilaments. The vestigial polypide includes the tentacle sheath, rudimentary lophophore, cerebral ganglion, and polypide retractors. The sensory part of 5HT-positive cells of the frontal membrane is dendrite-shaped and embedded in the inner organic layer of the ectocyst.
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