The first data on the vitellogenesis of paruterinid tapeworms: an ultrastructural study of Dictyterina cholodkowskii (Cestoda: Cyclophyllidea)
The present study provides the first ultrastructural data of the vitellogenesis in a cestode species of the cyclophyllidean family Paruterinidae, aiming to expand the limited data on the vitellogenesis in cyclophyllidean cestodes and to explore the potential of ultrastructural characters associated with vitellogenesis for phylogenetic and taxonomic studies of this order. The process of vitellocyte formation in Dictyterina cholodkowskii follows the general pattern observed in other tapeworms but exhibits several specific differences in the ultrastructure of vitelline cells. The vitellarium contains vitellocytes at various stages of maturation. The periphery of the vitellarium and the space between maturing vitellocytes are occupied by interstitial cells. Differentiation into mature vitellocytes is characterized by high secretory activity, which involves the development of granular endoplasmic reticulum, Golgi complexes, mitochondria and vitelline globules of various sizes. During vitellogenesis, the progressive fusion of these globules results in the formation of two large membrane-limited vitelline vesicles that eventually fuse into a single large vesicle. Mature vitellocytes are composed of a single vitelline vesicle, a high content of cytoplasmic organelles and have no nucleus. No traces of lipid droplets and glycogen granules are detected in the cytoplasm of mature vitellocytes, which might be related to biological peculiarities of this family, i.e. the release of eggs into environment within the tissues of the paruterine organ, which may serve as a source of nutrients for embryos.
KeywordsUltrastructure Vitellocytes Vitelline vesicles Cestode Cyclophyllidean Dictyterina cholodkowskii
The authors would like to thank the staff of the Laboratory of Electron Microscopy, Institute of Parasitology, České Budějovice, for the technical assistance. We are also grateful to Professor Kuizheng Cai, Professor Jialin Bai and the students Chuanshi Yan, Yuzhuo Xu, Janchiao Liu and Cuilan Wu (College of Life Science and Engineering, Northwest University for Nationalities, Lanzhou, People’s Republic of China) for their assistance in the field studies. The field trip of JM and BBG in Gansu Province was in the frames of a project supported by the National Science Foundation, USA (PBI awards no. 0818696 to Professor Janine N. Caira and no. 0818823 to Professor Kirsten Jensen). The present study used facilities developed at the Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, in the frames of the project CEBDER funded by Bulgarian National Science Fund, grant DOO2-15/17.02.2009.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national and institutional guidelines for the care and use of animals were followed.
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