Summary
The development of first-generation merozoites to second-generation schizonts and merozoites of Eimeria contorta in one of its natural hosts, the mouse, was investigated with the electron microscope. Merozoites inside a host cell show a marked U-shape and a degeneration of the inner pellicular membrane complex prior to transformation into schizonts. These processes closely resemble those seen in transforming sporozoites. In young schizonts with about 3–5 nuclei, the Golgi-adjuncts (structures of unknown function) form a large interconnected network.
Nuclear divisions in growing schizonts involve the formation of a centrocône, which develops in a pocket-like indentation of the nuclear envelope. At least one centriole is present immediately adjacent to this indentation. In a later stage, the centrocône forms a conical nuclear protrusion directed towards a merozoite-anlage. This developing merozoite contains anlagen of a conoid, of rhoptries, and of micronemes and a refractile body in addition to the nucleus, centrioles, and a Golgi-adjunct. The merozoite-anlage is limited by a triple unit membrane complex.
Schizonts give rise to 8–15 second-generation merozoites. Interesting features of these merozoites are the high number of micronemes, the finding of one single large mitochondrion per merozoite, and the occurrence of 26 subpellicular microtubules, i.e. the same number as in sporozoites of E. contorta. At the end of their development, merozoites come into direct contact with the host cell cytoplasm as the parasitophorous vacuole breaks down.
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References
Andreassen, J., Behnke, O.: Fine structure of merozoites of a rat coccidian Eimeria miyairii, with a comparison of the fine structure of other sporozoa. J. Parasit. 54, 150–163 (1968)
Colley, F.C.: Fine structure of sporozoites of Eimeria nieschulzi. J. Protozool. 14, 217–220 (1967)
Colley, F.C.: Fine structure of schizonts and merozoites of Eimeria nieschulzi. J. Protozool. 15, 374–382 (1968)
Dubremetz, J.-F.: Le conoide et les microtubules sous-pelliculaires du mérozoite d'Eimeria necatrix (Sporozoaire, Coccidiomorphe): étude au microscope électronique. C.R. Acad. Sci. (Paris) 272 D, 600–603 (1971a)
Dubremetz, J.-F.: L'ultrastructure du centriole et du centrocône chez la coccidie Eimeria necatrix. Etude au cours de la schizogonie. J. Microscop. (Paris) 12, 453–458 (1971b)
Dubremetz, J.-F.: Etude ultrastructurale de la mitose schizogonique chez la coccidie Eimeria necatrix (Johnson, 1930). J. Ultrastruct. Res. 42, 354–376 (1973)
Fernando, M.A.: Fine structure of the schizonts and merozoites of Eimeria acervulina in the chicken. J. Parasit. 60, 149–159 (1974)
Fernando, M.A., Remmler, O.: Fine structure of the first and second generation merozoites of Eimeria necatrix. Z. Parasitenk. 44, 133–137 (1974)
Haberkorn, A.: Zur Empfänglichkeit nicht spezifischer Wirte für Schizogonie-Stadien verschiedener Eimeria-Arten. Z. Parasitenk. 35, 156–161 (1970)
Haberkorn, A.: Zur Wirtsspezifität von Eimeria contorta n.sp. (Sporozoa: Eimeriidae). Z. Parasitenk. 37, 303–314 (1971)
Hammond, D.M.: Life cycles and development of coccidia. In: The Coccidia. (D.M. Hammond, ed.), p. 45–79. Baltimore and London: University Park Press and Butterworth 1973
Hammond, D.M., Roberts, W.L., Youssef, N.N., Danforth, H.D.: Fine structure of the intranuclear spindle poles in Eimeria callospermophili and E. magna. J. Parasit. 59, 581–584 (1973)
McLaren, D.J., Paget, G.E.: A fine structural study on the merozoite of Eimeria tenella with special reference to the conoid apparatus. Parasitology 58, 561–579 (1968)
Mehlhorn, H., Sénaud, J., Scholtyseck, E.: Sur l'ultrastructure des organites liés à la division nucléaire chez les coccidies Eimeria falciformis (Eimer, 1870) et Eimeria maxima (Tyzzer, 1929), au cours de la schizogonie et de la microgamétogenèse. C.R. Acad. Sci. (Paris) 275 D, 835–837 (1972)
Mehlhorn, H., Sénaud, J., Scholtyseck, E.: La schizogonie chez Eimeria falciformis (Eimer, 1870) Coccidie, Eimeriidae parasite de l'épithélium intestinal de la souris (Mus musculus). Protistologica 9, 269–291 (1973)
Müller, B.E.G.: In vitro development from sporozoites to first-generation merozoites in Eimeria contorta Haberkorn, 1971. A fine structural study. Z. Parasitenk. 47, 23–34 (1975)
Müller, B.E.G., Hammond, D.M., Scholtyseck, E.: In vitro development of first- and second-generation schizonts of Eimeria contorta Haberkorn, 1971 (Coccidia, Sporozoa). Z. Parasitenk. 41, 173–185 (1973)
Pellérdy, L., Haberkorn, A., Mehlhorn, H., Scholtyseck, E.: Die Feinstruktur der Schizonten und Merzoiten des Mäusecoccids Eimeria falciformis. Acta vet. Acad. Sci. hung. 21, 433–443 (1971)
Porchet-Henneré, E.: Considérations générales sur les processus de schizogonie chez les sporozoaires à la lumière des données de la microscopie électronique. Ann. Biol. 11, 413–426 (1972)
Roberts, W.L., Hammond, D.M.: Ultrastructural and cytological studies of the sporozoites of four Eimeria species. J. Protozool. 17, 76–86 (1970)
Roberts, W.L., Hammond, D.M., Speer, C.A.: Ultrastructural study of the intra- and extra-cellular sporozoites of Eimeria callospermophili. J. Parasit. 56, 907–917 (1970)
Ryley, J.F.: Ultrastructural studies on the sporozoite of Eimeria tenella. Parasitology 59, 67–72 (1969)
Scholtyseck, E.: Elektronenmikroskopische Untersuchungen über die Wechselwirkung zwischen dem Zellparasiten Eimeria perforans und seiner Wirtszelle. Z. Zellforsch. 61, 220–230 (1963)
Scholtyseck, E.: Electron microscope studies of the effect upon the host cell of various developmental stages of Eimeria tenella in the natural chicken host and in tissue culture. Acta vet. (Brno.) 38, 153–156 (1969)
Scholtyseck, E.: Ultrastructure. In: The Coccidia. (D.M. Hammond, ed.), p. 81–144. Baltimore and London: University Park Press and Butterworth 1973
Scholtyseck, E., Kepka, O., Piekarski, G.: Die Feinstruktur der Zoiten aus reifen Cysten des sog. M-Organismus (=Frenkelia spec.). Z. Parasitenk. 33, 252–261 (1970)
Sénaud, J.: Contribution à l'étude des sarcosporidies et des toxoplasmes (Toxoplasmea). Protistologica 3, 167–232 (1967)
Sénaud, J., Černa, Ž.: Etude en microscopie électronique des mérozoites et de la mérogonie chez Eimeria pragensis (Černa et Sénaud, 1968), Coccidie parasite de l'intestin de la sourie (Mus musculus). Ann. Stat. Biol. (Besse-en-Chandesse) 11, 221–242 (1968)
Sénaud, J., Černa, Ž.: Etude ultrastructurale des mérozoites et de la schizogonie des Coccidies (Eimeriina): Eimeria magna (Pérard, 1925) de l'intestin des lapins et E. tenella (Railliet et Lucet, 1891) des coecums des poulets. J. Protozool. 16, 155–165 (1969)
Speer, C.A., Hammond, D.M.: Development of Eimeria larimerensis from the Uinta ground squirrel in cell cultures. Z. Parasitenk. 37, 336–353 (1971)
Speer, C.A., Hammond, D.M., Anderson, L.C.: Development of Eimeria callospermophili and E. bilamellata from the Uinta ground squirrel Spermophilus armatus in cultured cells. J. Protozool. 17, 274–284 (1970)
Vetterling, J.M., Pacheco, N.D., Madden, P.A.: Ultrastructure of dormant, activated, and intracellular sporozoites of Eimeria adenoeides and E. tenella. J. Parasit. 59, 15–27 (1973)
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Part of a PhD thesis accepted by the Mathematisch-Naturwissenschaftliche Fakultät der Universität Bonn (D 5). With support from the Studienstiftung des Deutschen Volkes.
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Müller, B.E.G. Ultrastructural development of first- to second-generation merozoites in Eimeria contorta Haberkorn, 1971. Z. F. Parasitenkunde 47, 91–101 (1975). https://doi.org/10.1007/BF00382632
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DOI: https://doi.org/10.1007/BF00382632