Volume 49/Number 3/Abstract 4
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Acta Parasitologica, Vol.49, No. 3, 2004, 201-216
Zdzislaw Swiderski(1,2)*, Jordi Miquel(3), Sylvia Agostini(3,4), David Bruce Conn(5), Lidia Chomicz(6) and Barbara Grytner-Ziecina(2) - Differentiation and ultrastructure of the oncospheral envelopes of the cestode Joyeuxiella echinorhyncoides (Sonsino, 1889) (Cyclophyllidea, Dipylidiidae)

(1)W. Stefanski Institute of Parasitology, Polish Academy of Sciences, 51/55 Twarda Street, 00-818 Warsaw; (2)Department of General Biology and Parasitology, Medical University of Warsaw, 5 Chalubinskiego Street, 02-004 Warsaw, Poland. (3)Laboratori de Parasitologia, Facultat de Farmacia, Universitat de Barcelona, Av. Joan XXIII s/n, E-08028 Barcelona, Spain; (4)Laboratoire Parasites et Ecosystemes Mediterraneens, Faculte des Sciences et Techniques, Universite de Corse, F-20250 Corte, France. (5)School of Mathematical and Natural Sciences, Berry College, Mount Berry, Georgia 30149-5036, U.S.A.; (6)Department of Medical Biology, Medical University of Warsaw, 73 Nowogrodzka Street, 02-018 Warsaw, Poland
*Corresponding author: z.swider@twarda.pan.pl

In the preoncospheral stage of development of Joyeuxiella echinorhyncoides three primary embryonic envelopes are formed: (1) the capsule; (2) the outer envelope formed by two macromeres, and (3) the inner envelope originating from fusion of three mesomeres. Both the outer and inner envelopes of J. echinorhyncoides are therefore cellular in origin and syncytial in nature. Mature eggs of J. echinorhyncoides are spherical, measuring 47-60 38-48 um in diameter. Each uterine capsule contains one egg. Within fully formed eggs, the mature oncospheres, 25-27 um in diameter, are surrounded by five oncospheral or egg envelopes: (1) the outer shell, which originates from the initially delicate membranous capsule that becomes encrusted by the uterine-derived shell material that is deposited on it; (2) the outer envelope, still containing two large macromere nuclei; (3) the inner envelope, with three characteristic nuclei of mesomeres, and which secretes the electron-dense protective embryophore layer at its outer surface; (4) a unique type of "oncospheral membrane" that never becomes delaminated or detached from the rest of the inner envelope as a separate layer; and (5) a surface filament layer, composed of numerous elongated processes separated by cisternae containing material of very high electron density. The so-called "hook region membrane" covers only one pole of the mature oncosphere and is directly attached to the oncosphere surface. The ultrastructure of the oncospheral envelopes in J. echinorhyncoides shows some similarity to that described in the only other species of dipylidiid cestode examined to date, the cosmopolitan type-species, Dipylidium caninum. Differences between these two species include the absence of "hook region membrane", as well as bilayered and striated embryophore unique to D. caninum, and the undetached "oncospheral membrane" and unique "surface filament layer" and "interdigitating cisternae", characteristic of J. echinorhyncoides eggs.

KEY WORDS: Joyeuxiella echinorhyncoides, Cestoda, differentiation of oncospheral envelopes, ultrastructure

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