Summary
The microgametogenesis of Eimeria auburnensis from experimentally infected calves killed 16 to 18 days after inoculation was investigated with the electron microscope. Early microgametocytes had nuclei with compact nucleoli and relatively few electron-dense masses. In this stage, deep invaginations from the surface evidently served for the intake of nutrients from the parasitophorous vacuole. In older stages, the nuclei had no compact nucleoli and had more elctrondense material. An intranuclear fiber apparatus was present in some nuclei, apparently in an early stage of division. Nuclear division appeared in electron micrographs to occur by a kind of fission, in which the intranuclear fiber apparatus may participate. Numerous fissures appeared in the interior of the microgametocyte and the nuclei were arranged in irregular rows in association with these. Centrioles, either single or double, were observed between the nuclei and the membrane lining the fissures. Such nuclei often had an intranuclear fiber apparatus; one of the osmiophilic poles of this apparatus protruded outward from the nucleus in the vicinity of the centriole. Directly over this pole, electron-dense material, probably representing the anlage of the perforatorium, occurred immediately beneath the surface membrane of the fissure. As many as 9 closely arranged micropores were observed in this membrane in some specimens. In the nearly mature microgamete, the basal bodies of the flagella lay at the anterior end; the mitochondrion, with numerous, regularly arranged tubules began slightly posterior to this. The strongly osmiophilic, condensed nucleus was a little farther posterior; this remained connected by a narrow stalk with the uncondensed portion of the nucleus in the residual cytoplasm until the microgametes were almost completely mature. Usually, 2 flagella were present. Rarely, 3 flagella were observed, and evidence of a rudimentary middle flagellum was found in a number of specimens.
Zusammenfassung
Die Mikrogamogonie des Rindercoccids Eimeria auburnensis wurde mit Hilfe des EM untersucht. Junge Mikrogamonten haben Nuklei mit kompaktem Nukleolus und relativ wenig elektronendichten, unregelmäßig im Kernplasma verteilten Partikeln. Schon in jungen Mikrogamonten zeigen sich von der Oberfläche her tiefe, kanalartige Einstülpungen, die tief bis in das Zentrum des Gamonten führen und mit amorphem Material angefüllt sind, wie es in der parasitophoren Vakuole enthalten ist. In älteren Stadien ist der kompakte Nukleolus nicht mehr vorhanden. Dafür sind große Anteile des Kernplasmas stark elektronendicht. Innerhalb der Kerne werden intranukleäre Fibrillen beobachtet. Die Kernteilung erscheint im elektronenoptischen Bild als Zweiteilung, an der sich vermutlich die intranukleären Fibrillen beteiligen. Im Cytoplasma der Gamonten entstehen zahlreiche Spalträume, um die sich die Kerne anordnen. Centriolen in Ein- oder Zweizahl sind zwischen den einzelnen Kernen und den Membranen der Spalträume sichtbar. In diesem Stadium zeigen sich oft ebenfalls intranukleäre Fibrillen, die aus einem osmiophilen Pol in der Nähe der Centriolen entspringen. Oberhalb dieses spindelartigen Pols entwickelt sich eine osmiophile Platte unter der Membran des Spaltraumes. In dieser Membran können sich bis zu 9 Mikroporen dicht nebeneinander befinden. In der Spitze des langgestreckten Mikrogameten liegen die Basalkörper der Geißeln, weiter unterhalb ein besonders strukturiertes Mitochondrium und schließlich der langgestreckte, stark osmiophile Kern. Meistens werden an den Mikrogameten 2 Geißeln beobachtet, in wenigen Fällen sind aber 3 vorhanden und manchmal ergeben sich nur Hinweise auf eine dritte rudimentäre Geißel.
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Supported in part by Research Grant GB-5338 to Utah State University from the National Science Foundation, by the Deutsche Forschungsgemeinschaft, and by a Public Health Service Fellowship (5-Fl-GM-31,285-03) from the National Institute of General Medical Sciences. Published as Journal Paper Nr. 954, Utah Agricultural Experiment Station.
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Hammond, D.M., Scholtyseck, E. & Chobotar, B. Fine structural study of the microgametogenesis of Eimeria auburnensis . Z. F. Parasitenkunde 33, 65–84 (1969). https://doi.org/10.1007/BF00259570
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DOI: https://doi.org/10.1007/BF00259570