Abstract
The ultrastructure of ciliates carries important cytological, taxonomical, and evolutionary signals for these single-celled eukaryotic organisms. However, little ultrastructural data have been accumulated for most ciliate groups with systematic problems. In the present work, a well-known marine uronychiid, Diophrys appendiculata, was investigated using electron microscopy and a comparison with, and a discussion considering, phylogenetic analyses were made. The new findings primarily show that: (i) this species lacks the typical alveolar plate, bears cortical ampule-like extrusomes, and has microtubular triads in the dorsal pellicle, and thus exhibits some ultrastructural features in common with most of its previously studied congeners; (ii) each adoral membranelle before the level of frontal cirrus II/2 contains three rows of kinetosomes and each membranelle after the level of frontal cirrus II/2 contains four rows, which might be related with morphogenesis and could be considered as a distinctive character of Diophrys; (iii) some structural details of the buccal field, such as the extra-pellicular fibrils, pellicle, pharyngeal disks and microtubular sheet, were documented. In addition, based on the ultrastructural comparison of representatives, we discuss the differentiation between the subfamilies Diophryinae and Uronychiinae. A hypothetical systematic relationship of members in the order Euplotida based on a wide range of data is also provided.
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Data availability
A voucher slide (registration number: DJY2018030701) with protargol-stained specimens of the Qingdao population of Diophrys appendiculata has been deposited into the collection of the Laboratory of Protozoology (OUC), Qingdao, China. The SSU rDNA sequence of Diophrys appendiculata Qingdao population has been deposited in the GenBank database with accession number OK039190.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (32170446, 32030015, 31961123002) and the National Natural Science Foundation of Shanghai (21ZR1419000). The authors would like to express their gratitude to Prof. Weibo Song (Ocean University of China) for his generous help and advice in preparing the manuscript and Dr. Bing Ni (East China Normal University) for his helpful guidance in SEM and TEM. We thank Dr. Tengyue Zhang (Ocean University of China) for providing original cells for this study, and Dr. Tengteng Zhang (Ocean University of China) for her help with the molecular data.
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XP Fan conceptualized the project; JY Dong carried out the research; JY Dong, XP Fan, T Stoeck, YJ Liu, JY Ma and HG Ma helped with data interpretation, wrote, and revised the manuscript. All authors approved the final version of the manuscript.
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Special topic: Ciliatology.
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Dong, J., Liu, Y., Ma, J. et al. Ultrastructure of Diophrys appendiculata and new systematic consideration of the euplotid family Uronychiidae (Protista, Ciliophora). Mar Life Sci Technol 4, 551–568 (2022). https://doi.org/10.1007/s42995-022-00153-y
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DOI: https://doi.org/10.1007/s42995-022-00153-y
Keywords
- Ciliate
- Diophrys
- Euplotida
- Ultrastructure
- Uronychiidae