The nervous system in the cyclostome bryozoan Crisia eburnea as revealed by transmission electron and confocal laser scanning microscopy

Temereva, E. N.; Kosevich, I. A.

doi:10.1186/s12983-018-0295-4

Cited by 22 publications

(40 citation statements)

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“…It is possible that the reported lack of a lumen may be an artifact because sections were made when the polypide was retracted (which is clearly seen on their illustration: the tentacles are surrounded by tentacle sheath) and thus the tentacles could be deformed. A similar situation is presented in the images of the tentacle cross section in Temereva and Kosevich (). In the image of the tentacle cross section (fig.…”

Section: Discussionsupporting

confidence: 71%

“…According to our data, the projection of the subperitoneal cell stretched along the tentacle is narrow and filled with numerous microtubules. In cross section such design parallels the organization of an axon, and this is how this structure was interpreted by Gordon () and Temereva and Kosevich (). It is still unclear whether the subperitoneal cells might be considered as nerve cells.…”

Section: Discussionmentioning

confidence: 70%

“…It is still unclear whether the subperitoneal cells might be considered as nerve cells. Presence of subperitoneal neurites was not confirmed by recent immunocytochemical studies on P. articulata (Weber, Wanninger, & Schwaha, ) and C. eburnea (Temereva & Kosevich, ; Worsaae, Frykman, & Nielsen, ). In contrast, Schwaha, Handschuh, Ostrovsky, and Wanninger () described the inner peritoneal neurite bundles in Cinctipora elegans , although the authors encountered these neurites only in some specimens.…”

Section: Discussionmentioning

confidence: 70%

“…Before the present study, the tentacle structure in cyclostomes was examined with TEM methods in detail in C. eburnea by Nielsen and Riisgård (). There are also some TEM data on the tentacle structure in C. eburnea by Temereva and Kosevich () although their fig. 1a,b shows a colony of C. producta .…”

Section: Discussionmentioning

confidence: 99%

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Body cavities in bryozoans: Functional and phylogenetic implications

Shunatova

Tamberg

2019

Journal of Morphology

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Based on morphological evidence, Bryozoa together with Phoronida and Brachiopoda are traditionally combined in the group Lophophorata, although this view has been recently challenged by molecular studies. The core of the concept lies in the presence of the lophophore as well as the nature and arrangement of the body cavities. Bryozoa are the least known in this respect. Here, we focused on the fine structure of the body cavity in 12 bryozoan species: 6 gymnolaemates, 3 stenolaemates and 3 phylactolaemates.In gymnolaemates, the complete epithelial lining of the body cavity is restricted to the lophophore, gut walls, and tentacle sheath. By contrast, the cystid walls are composed only of the ectocyst-producing epidermis without a coelothelium, or an underlying extracellular matrix; only the storage cells and cells of the funicular system contact the epidermis. The nature of the main body cavity in gymnolaemates is unique and may be considered as a secondarily modified coelom. In cyclostomes, both the lophophoral and endosaccal cavities are completely lined with coelothelium, while the exosaccal cavity only has the epidermis along the cystid wall. In gymnolaemates, the lophophore and trunk cavities are divided by an incomplete septum and communicate through two pores. In cyclostomes, the septum has a similar location, but no openings. In Phylactolaemata, the body cavity is undivided: the lophophore and trunk coeloms merge at the bases of the lophophore arms, the epistome cavity joins the trunk, and the forked canal opens into the arm coelom. The coelomic lining of the body is complete except for the epistome, lophophoral arms, and the basal portions of the tentacles, where the cells do not interlock perfectly (this design probably facilitates the ammonia excretion). The observed partitioning of the body cavity in bryozoans differs from that in phoronids and brachiopods, and contradicts the Lophophorata concept. K E Y W O R D SBryozoa, coelom, excretion, Lophophorata, nutrient transport

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Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

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Body cavities in bryozoans: Functional and phylogenetic implications

Shunatova

Tamberg

2019

Journal of Morphology

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“…Cyclostomes and gymnolaemaetes almost invariably possess three distinct neurite bundles on the frontal side, suggesting that the three frontal ones (one medio‐frontal and two latero‐frontal) represent the ground pattern of Bryozoa. In the cyclostome Cinctipora elegans , the mediofrontal bundle terminates soon after its emergence or joins the latero‐frontal ones (Schwaha et al ., ), whereas it is continuous in the cyclostome Crisia eburnea (Temereva & Kosevich, ). Besides the three frontal neurite bundles, three abfrontal ones were detected in Crisia eburnea (Temereva & Kosevich, ) whereas only a single abfrontal nerve was detected in all gymnolaemates and the cyclostome Cinctipora elegans (Smith, ; Lutaud, ; Gordon, ; Nielsen & Riisgård, ; Schwaha & Wood, ; Weber et al ., ; Schwaha et al ., ).…”

Section: Character Evolutionmentioning

confidence: 99%

Key novelties in the evolution of the aquatic colonial phylum Bryozoa: evidence from soft body morphology

2020

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Molecular techniques are currently the leading tools for reconstructing phylogenetic relationships, but our understanding of ancestral, plesiomorphic and apomorphic characters requires the study of the morphology of extant forms for testing these phylogenies and for reconstructing character evolution. This review highlights the potential of soft body morphology for inferring the evolution and phylogeny of the lophotrochozoan phylum Bryozoa. This colonial taxon comprises aquatic coelomate filter-feeders that dominate many benthic communities, both marine and freshwater. Despite having a similar bauplan, bryozoans are morphologically highly diverse and are represented by three major taxa: Phylactolaemata, Stenolaemata and Gymnolaemata. Recent molecular studies resulted in a comprehensive phylogenetic tree with the Phylactolaemata sister to the remaining two taxa, and Stenolaemata (Cyclostomata) sister to Gymnolaemata. We plotted data of soft tissue morphology onto this phylogeny in order to gain further insights into the origin of morphological novelties and character evolution in the phylum. All three larger clades have morphological apomorphies assignable to the latest molecular phylogeny. Stenolaemata (Cyclostomata) and Gymnolaemata were united as monophyletic Myolaemata because of the apomorphic myoepithelial and triradiate pharynx. One of the main evolutionary changes in bryozoans is a change from a body wall with two well-developed muscular layers and numerous retractor muscles in Phylactolaemata to a body wall with few specialized muscles and few retractors in the remaining bryozoans. Such a shift probably pre-dated a body wall calcification that evolved independently at least twice in Bryozoa and resulted in the evolution of various hydrostatic mechanisms for polypide protrusion. In Cyclostomata, body wall calcification was accompanied by a unique detachment of the peritoneum from the epidermis to form the hydrostatic membraneous sac. The digestive tract of the Myolaemata differs from the phylactolaemate condition by a distinct ciliated pylorus not present in phylactolaemates. All bryozoans have a mesodermal funiculus, which is duplicated in Gymnolaemata. A colonial system of integration (CSI) of additional, sometimes branching, funicular cords connecting neighbouring zooids via pores with pore-cell complexes evolved at least twice in Gymnolaemata. The nervous system in all bryozoans is subepithelial and concentrated at the lophophoral base and the tentacles. Tentacular nerves emerge intertentacularly in Phylactolaemata whereas they partially emanate directly from the cerebral ganglion or the circum-oral nerve ring in myolaemates. Overall, morphological evidence shows that ancestral forms were small, colonial coelomates with a muscular body wall and a U-shaped gut with ciliary tentacle crown, and were capable of asexual budding. Coloniality resulted in many novelties including the origin of zooidal polymorphism, an apomorphic landmark trait of the Myolaemata.Biological Reviews 95 (2020) 696-729

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Unusual lophophore innervation in ctenostome Flustrellidra hispida (Bryozoa)

2022

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Since ctenostomes are traditionally regarded as an ancestral clade to some other bryozoan groups, the study of additional species may help to clarify questions on bryozoan evolution and phylogeny. One of these questions is the bryozoan lophophore evolution: whether it occurred through simplification or complication. The morphology and innervation of the ctenostome Flustrellidra hispida (Fabricius, 1780) lophophore have been studied with electron microscopy and immunocytochemistry with confocal laser scanning microscopy. Lophophore nervous system of F. hispida consists of several main nerve elements: cerebral ganglion, circumoral nerve ring, and the outer nerve ring. Serotonin‐like immunoreactive perikarya, which connect with the circumoral nerve ring, bear the cilium that directs to the abfrontal side of the lophophore and extends between tentacle bases. The circumoral nerve ring gives rise to the intertentacular and frontal tentacle nerves. The outer nerve ring gives rise to the abfrontal neurites, which connect to the outer groups of perikarya and contribute to the formation of the abfrontal tentacle nerve. The outer nerve ring has been described before in other bryozoans, but it never contributes to the innervation of tentacles. The presence of the outer nerve ring participating in the innervation of tentacles makes the F. hispida lophophore nervous system particularly similar to the lophophore nervous system of phoronids. This similarity allows to suggest that organization of the F. hispida lophophore nervous system may reflect the ancestral state for all bryozoans. The possible scenario of evolutionary transformation of the lophophore nervous system within bryozoans is suggested.

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The nervous system in the cyclostome bryozoan Crisia eburnea as revealed by transmission electron and confocal laser scanning microscopy

Cited by 22 publications

References 50 publications

Body cavities in bryozoans: Functional and phylogenetic implications

Body cavities in bryozoans: Functional and phylogenetic implications

Key novelties in the evolution of the aquatic colonial phylum Bryozoa: evidence from soft body morphology

Unusual lophophore innervation in ctenostome Flustrellidra hispida (Bryozoa)

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