Acta Parasitologica, Vol. 52, No. 2, 2007, 114–126. DOI: 10.2478/s11686-007-0020-5 Zdzisław Świderski1,2*, Jordi Miquel3, Lassad Neifar4 and John S. Mackiewicz5 – Ultrastructural and cytochemical studies on vitellogenesis
in the trypanorhynch cestode Parachristianella trygonis Dollfus, 1946 (Eutetrarhynchidae) 1W. Stefański Institute of Parasitology, Polish Academy of Sciences, 51/55 Twarda Street, 00-818 Warsaw, Poland; 2Department of General Biology and Parasitology, Warsaw Medical University, 5 Chałubińskiego Street, 02-004 Warsaw, Poland; 3Laboratori de Parasitologia, Departament de Microbiologia i Parasitologia Sanitàries, Facultat de Farmàcia, Universitat de Barcelona,
Av. Joan XXIII, sn, 08028 Barcelona, Spain; 4Département de Biologie, Faculté des Sciences de Sfax, 3018 Sfax, Tunisie; 5Department of Biological Sciences, State University of New York at Albany, Albany, N.Y. 12222, USA
*Corresponding author: z.swider@twarda.pan.pl
ABSTRACT
During vitellogenesis in Parachristianella trygonis (Trypanorhyncha, Eutetrarhynchidae) we distinguished four stages: (1)
gonial or stem cell stage; (2) early differentiation stage concentrated on protein synthetic activity and shell-globule formation;
(3) advanced differentiation stage with main cell activity concentrated on carbohydrate synthesis (glycogenesis) and massive
glycogen storage in the form of α-glycogen rosettes and β-glycogen particles; and finally (4) mature vitellocyte stage. Early
vitellocyte maturation is characterised by: (1) an increase in cell volume; (2) extensive development of large, parallel cisternae
of GER that produce proteinaceous granules; (3) development of Golgi complexes engaged in packaging this material; (4)
continuous enlargement of proteinaceous granules within vacuoles and their transformation into shell-globule clusters composed
of heterogeneous material. Cytochemical staining with periodic acid-thiosemicarbazide-silver proteinate for polysaccharides
indicated a strongly positive reaction for the presence of α-glycogen rosettes and β-glycogen particles in the advanced
stage of vitellocyte maturation. Both protein synthesis for shell-globule formation and carbohydrate synthesis or glycogenesis,
important storage of nutritive reserves for the developing embryos, observed during cytodifferentiation of P. trygonis vitellocytes
overlap in time to some extent. Mature vitelline cells are very rich in three types of cell inclusions accumulated in large
amounts in their cytoplasm: (1) shell-globule clusters, playing an important role in egg-shell formation; (2) numerous large lipid
droplets, as well as a high accumulation of lipid and α-glycogen rosettes and β-glycogen particles that undoubtedly represent
important nutritive reserves for the developing embryos. Despite the fact that the type of vitellogenesis and ultrastructure of
the mature vitellocyte in P. trygonis appears to differ to some extent from those of three other trypanorhynch species, its general
pattern and ultrastructure greatly resembles those observed in other lower cestodes. Factors that may have contributed to
the qualitative and quantitative variation in lipids during vitellogenesis among the four species of Trypanorhyncha, are identified
and discussed.
KEY WORDS: Cestoda, Trypanorhyncha, Parachristianella trygonis, vitellogenesis, ultrastructure, cytochemistry