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Junctional complexes in the inner cyst tissue of the cysticercoid of Hymenolepis diminuta (Cestoda)

Published online by Cambridge University Press:  06 April 2009

K. Sylvia Richards  and
C. Arme
K. Sylvia Richards
Affiliation:
Parasitology Research Laboratory, Department of Biological Sciences, University of Keele, Keele, Staffs. ST5 5BG
C. Arme
Affiliation:
Parasitology Research Laboratory, Department of Biological Sciences, University of Keele, Keele, Staffs. ST5 5BG
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Summary

The inner cyst tissue development is anteriad and centripetal. The cells produce lamellar extensions which assume parallel alignment. The first contact points (approximately 4 days post-infection) establish heptalaminar (gap) junctions. Lamellar attenuation results in a decreased intercellular space, and at 5–6 days pentalaminar junctions (with fused outer plasmalemma leaflets to give an electron-dense, approximately 3 nm wide O–O line) occur. This is the first maturation (Ml) stage. The O–O lines are permeable to lanthanum, and evidence of their possible transformation from heptalaminar junctions is presented. Continued lamellar attenuation, associated with scolex retraction and subsequent growth, results in cytoplasmic occlusion and contact between the inner leaflets of the same lamella. The resultant electron-dense I–I line is approximately 3 nm wide; the O–O line is now less electron-dense and thinner (approximately 2 nm). This final maturation (M2) stage, resembling vertebrate myelin, occurs over limited areas; closely adjacent regions either remaining at the M1 stage, or not displaying junctional complexes. Since in vivo and in vitro excystment can occur before the M2 stage, the inner cyst tissue is not considered to be protective against the definitive host. That the tissue may function in limiting nutrient flow, thus regulating the size of the presumptive adult, is discussed.

Type
Research Article
Information
Parasitology , Volume 87 , Issue 2 , October 1983 , pp. 295 - 306
Copyright
Copyright © Cambridge University Press 1983

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