Electron microscope study on vitellogenesis in Catenotaenia pusilla (Goeze, 1782) (Cyclophyllidea, Catenotaeniidae)

The vitellogenesis in Catenotaenia pusilla was examined by means of electro n microscopy. Mature vitelline follicles consist of cells in various stages of development, progressing from immature cells of genial type near the pe riphery to mature vitellocytes towards the centre. Maturation is characteri sed by: (1) increase in cell volume; (2) extensive development of large par allel cisternae of GER, the vitelline material producing units; (3) develop ment of Golgi complexes engaged in vitelline material package; (4) continuo us fusion of small vesicles into larger vitelline vesicles and fusion of th ese into 3 very large vesicles, which are characteristic for mature vitello cytes of this tapeworm. Vitellogenesis in C. pusilla is compared with that in other cestodes. Some conclusions concerning the interrelationship betwee n the vitellogenesis pattern and the type of embryogenesis are drawn and di scussed.