Volume 49/Number 2/Abstract 03
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Acta Parasitologica, Vol.49, No. 2, 2004, 108-115
Zdzislaw Swiderski (1,2)*, David Bruce Conn(3), Jordi Miquel(4) and Daniel Mlocicki(1) - Fertilization in the cestode Gallegoides arfaai (Mobedi et Ghadirian, 1977) Tenora et Mas-Coma, 1978 (Cyclophyllidea, Anoplocephalidae)
(1)W. Stefanski Institute of Parasitology, Polish Academy of Sciences, 51/55 Twarda Street, 00-818 Warsaw; (2)Department of General Biology and Parasitology, Warsaw Medical University, 5 Chalubinskiego Street, 02-004 Warsaw, Poland; (3)School of Mathematical and Natural Sciences, Berry College, Mount Berry, Georgia 30149-5036, U.S.A.; (4)Laboratori de Parasitologia, Facultat de Farmacia, Universitat de Barcelona, Av. Joan XXIII s/n, E-08028 Barcelona, Spain
*Corresponding author: z.swider@twarda.pan.pl

Fertilization in the anoplocephalid cestode Gallegoides arfaai with uniflagellate spermatozoa was examined by means of light and transmission electron microscopy. Fertilization in this species occurs in the oviduct lumen or in the fertilization canal proximal to the ootype, where the formation of the embryonic capsule precludes sperm contact with the oocyte. Cortical granules are not present in the cytoplasm of oocytes of this species. However, two other types of large bodies containing granular material, one of homogeneous moderate electron density and one of heterogeneous moderate electron density, are present in the perinuclear cytoplasm of the oocytes. Spermatozoa coil spirally around the oocytes and syngamy occurs by lateral fusion of oocyte and sperm plasma membranes. In the ootype, one vitellocyte associates with the fertilized oocyte, forming a membranous capsule which encloses both cell types. In this stage, spirally coiled sperm flagella adhere partly to the external oocyte surfaces, and partially enter into the perinuclear cytoplasm. Usually, several loops of the spermatozoon occur within the oocyte cytoplasm. The electron-dense sperm nucleus becomes progressively electron-lucent within the oocyte cytoplasm after entry. Simultaneously with chromatin decondensation, the elongate sperm nucleus changes shape, forming a spherical male pronucleus, which attains the size of the female pronucleus. Cleavage begins immediately after pronuclear fusion.

KEY WORDS: Gallegoides arfaai, Cestoda, Cyclophyllidea, Anoplocephalidae, fertilization, ultrastructure

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