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Ultrastructure of oncospheral envelopes and their differentiation in the cestode, Dicranotaenia coronula [Dujardin, 1845] [Cyclophyllidea, Hymenolepididae]

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Chomicz L., Swiderski Z., Grytner-Ziecina B.

Acta Parasitologica

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1995

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tom 40

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nr 1

Studies of the ultrastructure of oncospheral envelopes and their differentiation in the hymenolepidid cestode Dicranotaenia coronula in utero revealed four main envelopes: (1) capsule, (2) outer envelope, (3) inner envelope with a thin, electron-dense embryophore, and (4) oncospheral membrane. An additional hemispherical calotte, the hook region membrane covers one pole of the oncosphere and is attached to its surface. Both the outer and inner envelope represent syncytial layers which contain large, flattened nuclei of blastomeres which participated in their formation: nuclei of macromeres in the outer, and nuclei of mesomeres in the inner envelope. The granular cytoplasm of the both envelopes contains a large amount of free ribosomes, numerous mitochondria and several lipid droplets. The primary inner envelope of the early embryo forms in the later stage of embryogenesis its two derivatives: the embryophore and the oncospheral membrane. The hook region membrane oryginates from a syncytial binucleate complex by delamination of its cytoplasmic plate. Both the ultrastructural features of oncospheral envelopes and mode of their differentiation are compared with those described previously in the other hymenolepidids with aquatic and terrestrial life cycles. The ultrastructure of the oncospheral envelopes in D. coronula is discussed in relation to its life cycle and to environmental conditions in which the infective eggs remain for a certain period of time, until eaten by benthal ostracods, the intermediate hosts of D. coronula.

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Ultrastructural studies on the oncospheral envelopes of hymenolepidid cestode, Wardium aequabile [Rudolphi, 1810] Spassky et Spasskaya, 1954, in the final stage on infective egg formation

100%

Chomicz L., Cielecka D., Walski M., Czubaj A.

Acta Parasitologica

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1997

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tom 42

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nr 1

The oncospheral envelope morphology, representing an useful criterion in the taxonomy of cestodes, were examined, at the ultrastructural level, in hymenolepidid Wardium aequabile, developing in hosts connected with an aquatic environment. Adult specimens of the cestode from swan, processed for ТЕМ, were analysed. Inside the uterus, around each oncosphere the following envelopes were observed: the outer and the inner envelopes, the embryophore and the oncospheral membrane. The lumenal side of the uterus forms compact layer, rich in cytoplasmic components and intruding between individual eggs. There were certain features characteristic for W. aequabile: (1) details of ultrastructure of the outer envelope and uterine wall; (2) the embryophore with thick electron-dense core layer; (3) the long hooked appendage at each pole of the egg, inside the inner envelope, with the embryophore penetrating into the appendages. Significance of ultrastructural features of W. aequabile in relation to life cycle of the cestode is discussed and, differences and similarity with other hymenolepidids developing in hosts in aquatic environment are presented.

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Ultrastructure of the infective eggs of the hymenolepidid cestode, Ditestolepis tripartita [Zarnowski, 1955], a parasite of shrews

100%

Swiderski Z., Tkach V.

Acta Parasitologica

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1997

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tom 42

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nr 1

The ultrastructure of infective eggs of the hymenolepidid cestode, Ditestolepis tripartita, a parasite of shrews, was examined with emphasis on cellular organisation of mature oncospheres. Each hexacanth larva is surrounded by three main egg envelopes: thin layer of amorphous outer envelope, relatively thick layer of inner envelope with an embryophore and a delicate oncospheral membrane. The outer and inner envelopes of infective eggs of D. tripartita are usually amorphous; the embryophore is relatively thin and moderately electron-dense. Five major types of oncospheral cells have been distinguished. These consist of: (1) about ten germinative cells; (2) about 30 somatic cells (= myocytons of somatic and hook muscles); (3) a bi-nucleate medullary centre (= tegumental perikaryon); (4) a bi-nucleate, U-shaped penetration gland and (5) two cells of neurosecretory type with characteristic dense-cored vesicles. The hook-muscle system with complex interconnections between different muscle fibers provides a structural basis for coordinated hook action.

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Differentiation and ultrastructure of the oncospheral envelopes in the hymenolepidid cestode Staphylocystoides stefanskii [Zarnowski, 1954]

100%

Tkach V. V., Swiderski Z.

Acta Parasitologica

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1998

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tom 43

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nr 4

Ultrastructure of the oncospheral envelopes in developing and fully formed eggs of the hymenolepidid cestode, Staphylocystoides stefanskii (Zarnowski, 1954), is described. The uterus in this species is saccular, with deep infoldings of the uterine wall which form pocket-like structures. The uterine wall is composed by a flat syncytial uterine epithelium containing elongated nuclei with prominent nucleoli. The differentiating and mature oncospheres are surrounded by three envelopes: (1) an outer envelope; (2) an inner envelope consisting of three layers - an extraembryophoral cytoplasmic layer, a dense and relatively thick embryophore, and an intraembryophoral cytoplasmic layer; (3) a thin oncospheral membrane, surrounding the oncosphere. The outer envelope usually contains 2 nuclei in the preoncospheral stage, however, no nuclei were observed in this layer in the fully formed eggs. The inner envelope shows in sectioned material 1-2 nuclei in its intraembryophoral layer. The extraembryophoral layer of the inner envelope increases in thickness during the egg maturation. The embryophore was initially discontinuous, formed by the blocks of the electron-dense substance, and situated directly under the outer limiting membrane of the inner envelope. Later the neighbouring blocks fuse together and finally produce a continuous dense layer of embryophore. The embryophore remains slightly vacuolised for some time and finally forms a thick homogeneously electron-dense layer. The oncospheral membrane appears striated on the high-power micrographs. The ultrastructure of oncospheral envelopes in S. stefanskii is compared with those in other mammalian hymenolepidids.

Ograniczanie wyników

4 Acta Parasitologica

3 Swiderski Z.

2 Chomicz L.

1 Cielecka D.

1 Czubaj A.

1 Grytner-Ziecina B.

1 Tkach V.

1 Tkach V. V.

1 Walski M.

1 1998

2 1997

1 1995

Ultrastructure of oncospheral envelopes and their differentiation in the cestode, Dicranotaenia coronula [Dujardin, 1845] [Cyclophyllidea, Hymenolepididae]

Ultrastructural studies on the oncospheral envelopes of hymenolepidid cestode, Wardium aequabile [Rudolphi, 1810] Spassky et Spasskaya, 1954, in the final stage on infective egg formation

Ultrastructure of the infective eggs of the hymenolepidid cestode, Ditestolepis tripartita [Zarnowski, 1955], a parasite of shrews

Differentiation and ultrastructure of the oncospheral envelopes in the hymenolepidid cestode Staphylocystoides stefanskii [Zarnowski, 1954]