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1

Ultrastructure of vitellocytes in the cestode Progrillotia pastinacae Dollfus, 1946 [Trypanorhyncha, Progrillotiidae]

100%
Swiderski Z., Miquel J., Mlocicki D., Neifar L., Grytner-Ziecina B., Mackiewicz J. S.
Acta Parasitologica
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2006
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tom 51
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nr 3
The present study describes the ultrastructure of mature vitellocytes of the trypanorhynch cestode Progrillotia pastinacae Dollfus, 1946 (Progrillotiidae), a parasite of the common stingray Dasyatis pastinaca (Linnaeus, 1758) (Dasyatidae). The vitelline cells of this species measure about 24 μm in length and about 20 μm in width. They have small, elongated, slightly lobulated nuclei, about 4–5 μm in length, with large dense elongated nucleoli and numerous irregularly-shaped dense clumps of heterochromatin. The extensive cytoplasm is rich in numerous cell organelles and cell inclusions. While the perinuclear cytoplasm contains numerous long parallel cisternae of GER, ribo-and polyribosomes, several Golgi complexes and mitochondria, the peripheral cytoplasm contains predominantly three types of cell inclusions: a great number of large lipid droplets, several shell globule clusters, and a very small amount of glycogen-like particles. The most characteristic features of vitellocytes in P. pastinacae are having almost no traces of glycogen and the great number of large, highly osmiophobic lipid droplets representing saturated fatty acids. The presence of large amounts of lipids also in two other trypanorhynchs, Grillotia erinaceus (Beneden, 1858) Guiart, 1927 and Dollfusiella spinulifera (Beveridge et Jones, 2000) Beveridge, Neifar et Euzet, 2004, is in strong contrast to the condition in the most evolved cestodes, Cyclophyllidea, that usually show no trace of lipids.
2

Ultrastructure of the vitellarium in the digeneans Phyllodistomum angulatum (Plagiorchiida, Gorgoderidae) and Azygia lucii (Strigeida, Azygiidae)

80%
Poddubnaya L. G., Brunanska M., Swiderski Z., Gibson D. I.
Acta Parasitologica
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2012
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tom 57
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nr 3
Fine structural features of the vitellarium of two digeneans, Phyllodistomum angulatum and Azygia lucii, are documented and compared with those of other digenean species. The cytodifferentiation of immature vitelline cells (vitellocytes) assumes the production and subsequent accumulation in their cytoplasm of several inclusions. Mature vitelline cells of P. angulatum are characterized by the presence of vitelline clusters (∼2.7 μm in diameter, with ∼100 vitelline globules of ∼0.35 μm in diameter) and osmiophobic, saturated lipid droplets (∼2-3 μm in diameter), and in A. lucii vitelline clusters of the same diameter include much fewer vitelline globules (∼50 globules of ∼0.5 μm in diameter), osmiophilic lipid droplets and α-glycogen. In both P. angulatum and A. lucii, interstitial cells are also present within the vitellarium. Two types of contact sites (septate and tight junctions) between adjoining interstitial cells also occur in both digenean species. Judging from the present and previous ultrastructural studies, it is suggested that there are three potential discriminatory characters of the digenean vitellarium (the number of different types of cell components within the vitellarium, the presence and type of junctional complexes between these cells, and the isolation of the vitellarium from the surrounding tissue) which may prove useful for a better understanding of the biology and evolutionary history of the different digenean groups.
3

An experimental study of egg assembly in the monogenean [platyhelminth] skin parasite Entobdella soleae, using a fast preservation technique and transmission electron microscopy

80%
Tappenden T., Kearn G. C.
Acta Parasitologica
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1999
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tom 44
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nr 1
Stages in the assembly of the egg in the monogenean skin parasite Entobdella soleae have been studied using a fast preservation technique for transmission electron microscopy. The first event is the release by the germarium of a fertilised oocyte, which travels to the ootype followed by many vitelline cells. There are two types of Mehlis' gland and the secretion from one of these (beta) is thought to promote the release of the vitelline droplets, which fuse peripherally in the distal tetrahedral chamber of the ootype to produce the eggshell. Initially, the zygote lodges in the distal corner of the chamber, perhaps held in place by cortical granule material, and prevents shell deposition in this corner. However, this is temporary, and when the zygote leaves the corner the opercular eggshell is laid down. The egg appendage is assembled in the proximal tubular part of the ootype and the adhesive droplets on the appendage are derived from the second (alpha) type of Mehlis' secretion.
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