Abstract
The study of the microscopic anatomy of the larvae of Entoprocta is interesting in the context of determining the phylogenetic position of this group. It is assumed that the comparison of the organization of larval stages of entoprocts with different life cycle stages of other taxa (bryozoans, cycliophorans, mollusks) may help to find common features in their organization, indicating possible close relationships of these groups. There are few data on the microscopic anatomy of the larvae of entoprocts. The fine structure of larvae of only two solitary species, Loxosomella murmanica and Loxosoma pectinaricola, has been described in detail. Here we described the ultrastructure of the swimming larva of colonial species Barentsia gracilis. Our data clarify some details of the structure of entoproct larvae. The cuticle of larval stages is similar to that of adults. The prototroch is represented by two rows of ciliated cells. The apical and frontal ganglia are devoid of a central neuropil, which distinguishes them from the ganglion of adults. Ganglia include not only nerve cells but also muscle cells. The digestive tract of larvae and adults is similar not only at the histological level but also at the ultrastructural level. Three pairs of pedal glands include cells with electron-dense granules and cells with vacuoles with granular contents. These glands probably secrete different components of mucus. Each of the protonephridia consists of two terminal cells that pass into their own canals, which then fuse together and open by the nephropore on the hyposphere.
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The data that support the findings of this study are available from the corresponding author, Borisanova A.O., upon request.
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Acknowledgements
The authors are grateful to the management of Pertsov White Sea Biological Station of Lomonosov Moscow State University (WSBS MSU) and the center of microscopy of WSBS for opportunity to conduct the research and especially to WSBS diving team for their assistance in samples collecting. SEM studies and TEM studies were carried out at the Shared Research Facility “Electron Microscopy in Life Sciences” at Moscow State University (Unique Equipment “Three-dimensional electron microscopy and spectroscopy”). The authors are thankfull to the Reviewers for their thoughtful comments.
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This work was supported by the Russian Science Foundation (Grant number 23-14-00020).
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O.I. collected and fixed the material. Both authors participated in the preparation of the material for research by transmission electron microscopy and in obtaining the results. A.B. wrote the main manuscript text and prepared all figures.
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Borisanova, A.O., Ivanova, O.V. Ultrastructure of a swimming-type larva of Barentsia gracilis (Entoprocta, Coloniales). Zoomorphology (2024). https://doi.org/10.1007/s00435-024-00657-4
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DOI: https://doi.org/10.1007/s00435-024-00657-4