Hostname: page-component-586b7cd67f-dsjbd Total loading time: 0 Render date: 2024-12-02T20:59:56.600Z Has data issue: false hasContentIssue false
  • English
  • Français

An investigation of the mechanism of infection by digenetic trematodes: the penetration of the miracidium of Fasciola hepatica into its snail host Lymnaea truncatula

Published online by Cambridge University Press:  06 April 2009

R. A. Wilson ,
P. Pullin  and
Jean Denison
R. A. Wilson
Affiliation:
Department of Biology, University of York, Heslington, York
P. Pullin
Affiliation:
Department of Biology, University of York, Heslington, York
Jean Denison
Affiliation:
Department of Biology, University of York, Heslington, York
Get access Rights & Permissions [Opens in a new window]

Extract

The penetration barrier presented to the miracidium by the snail epithelium can be divided into three layers. The chemical composition and physical configuration of the outermost of these plays an important part in the initial attachment response of the miracidium. Attachment can be stimulated in the absence of the snail by pure chemicals in solution. However, the surface to which the miracidium attaches must have the correct physical configuration otherwise the miracidium is unable to form a stable attachment.

In vivo, the miracidial body begins to contract and relax following attachment to the snail. This coincides with the start of secretion by the apical gland and accessory gland cells. The snail's columnar epithelium is rapidly cytolysed so that 10 min after attachment the anterior of the miracidium has reached the underlying connective tissues.

As the miracidium penetrates the snail, its ciliated epithelial cells are shed in sequence from anterior to posterior. This shedding removes a protective barrier against osmosis which is probably the acid mucopolysaccharide present in the epithelial cells. The mechanism of shedding is not understood but involves the reversal of binding by the desmosomal mucosubstance which attaches the epithelial cells to surrounding intercellular ridges.

The miracidium metamorphoses into the sporocyst as it penetrates the snail, by forming a new body surface. The material for this is extruded from the vesiculated cells which lie beneath the musculature of the body wall. The process of surface formation coincides with cell shedding and moves backwards as cells are shed. At not more than 2·5 h after attachment the extruded cytoplasm forms a thin continuous layer over the surface of the organism. Contacts with underlying cells appear to have been broken and the cytoplasm is underlain by a thin fibrous basal lamella. In the first 24 h after penetration the surface of this syncytium becomes thrown into folds and metamorphosis into the sporocyst can be considered complete.

Type
Research Article
Information
Parasitology , Volume 63 , Issue 3 , December 1971 , pp. 491 - 506
Copyright
Copyright © Cambridge University Press 1971

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Barlow, C. H. (1925). The life cycle of the human intestinal fluke Fasciolopsis buski. American Journal of Hygiene. Monographic Series No. 4.Google Scholar
Campbell, W. C. & Todd, A. C. (1955). Behaviour of the miracidium of Fascioloides magna (Bassi, 1875) Ward, 1917 in the presence of a snail host. Transactions of the American Microscopical Society 74, 342–7.CrossRefGoogle Scholar
Clegg, J. A. (1969). Skin penetration by cercariae of the bird schistosome Austrobilharzia terrigalensis: the stimulatory effect of cholesterol. Parasitology 59, 973–89.CrossRefGoogle ScholarPubMed
Dawes, B. (1960). A study of the miracidium of Fasciola hepatica and an account of the mode penetration of the sporocyst into Lymnaea truncatula. Libro Homenaje al Dr Eduardo Caballero y Caballero 95–111. Mexico: Escuela Nacional de Ciensias Biologicas.Google Scholar
Mattes, O. (1949). Wirtsfindung, Invasionsvorgang, und Wirtsspezifität beim Fasciola—Miracidium. Zeitschrift für Parasitenkunde 14, 320–63.CrossRefGoogle Scholar
Mcinnis, A. J. (1965). Responses of Schistosoma mansoni miracidia to chemical attractants. Journal of Parasitology 51, 731–46.CrossRefGoogle Scholar
Moscona, A. (1952). Cell suspensions from organ rudiments of chick embryos. Experimental Cell Research 3, 535–9.CrossRefGoogle Scholar
Paul, J. (1965). Cell and Tissue Culture. Edinburgh and London: Livingstone.Google Scholar
Pearse, A. G. E. (1961). Histochemistry, Theoretical and Applied. London: Churchill.Google Scholar
Pullin, R. S. V. (1970). A study of the environment of larval Fasciola hepatica L. with a view to developing a defined medium for in vitro culture. D. Phil thesis, University of York.Google Scholar
Rappaport, C. & Howze, G. B. (1966). Dissociation of adult mouse liver by sodium tetra-phenylboron, a potassium complexing agent. Proceedings of the Society for Experimental Biology and Medicine 121, 1010–16.CrossRefGoogle ScholarPubMed
Richardson, K. C., Jarett, L. & Finke, E. H. (1960). Embedding in epoxy resins for ultrathin sectioning in electron microscopy. Stain Technology 35, 313–23.CrossRefGoogle ScholarPubMed
Southgate, V. R. (1970). Observations on the epidermis of the miracidium and on the formation of the tegument of the sporocyst of Fasciola hepatica. Parasitology 61, 177–90.CrossRefGoogle ScholarPubMed
Targett, G. A. T. & Robinson, D. L. H. (1964). Observations on the in vitro survival of miracidia of Schistosoma mansoni. Annals of Tropical Medicine and Parasitology 58, 453–6.CrossRefGoogle ScholarPubMed
Wilson, R. A. (1968). An investigation into the mucus produced by Lymnaea truncatula, the snail host of Fasciola hepatica. Comparative Biochemistry and Physiology 24, 629–33.CrossRefGoogle ScholarPubMed
Wilson, R. A. (1969 a). Fine structure of the tegument of the miracidium of Fasciola hepatica L. Journal of Parasitology 55, 124–33.CrossRefGoogle ScholarPubMed
Wilson, R. A. (1969 b). Fine structure and organisation of the musculature in the miracidium of Fasciola hepatica. Journal of Parasitology 55, 1153–61.CrossRefGoogle ScholarPubMed
Wilson, R. A. (1970). Fine structure of the nervous system and specialised nerve endings in the miracidium of Fasciola hepatica. Parasitology 60, 399–410.CrossRefGoogle ScholarPubMed
Wilson, R. A. (1971). Gland cells and secretions in the miracidium of Fasciola hepatica. Parasitology 63, 225–31.CrossRefGoogle ScholarPubMed
Wilson, R. A. & Denison, J. (1970). Short chain fatty acids as stimulants of turning activity by the miracidium of Fasciola hepatica. Comparative Biochemistry and Physiology 32, 511–17.CrossRefGoogle ScholarPubMed