Summary
The uterus cells of Microdalyellia fairchildi which are rich in agranular ER produce a vesicular substance released from the cells at the beginning of egg-shell formation. The lumenal border of the cells is thrown into lamellae like and partly branched outfoldings which inter-digitate. After filling of the uterus with the oocyte and several vitelline cells the outfoldings are stretched to form a smooth inner wall. A plenty of shell droplets are set free by the vitelline cells. The droplets accumulate at the inner surface of the uterus and coalesce along a thin layer of uterus secretion. Lower amounts of uterus secretion do not achieve a uniform inner lining of the uterus wall. The initially thin capsule wall is thickened by fusing with further shell droplets and subsequently becomes resistent by sclerotization.
Zusammenfassung
Die Zellen des Uterus von Microdalyellia fairchildi, die durch ein reichlich entwickeltes ER ausgezeichnet sind, produzieren ein bläschenartiges Sekret, das am Beginn der Eibildung ausgeschieden wird. Die innere Oberfläche der Zellen bildet zahlreiche, teils verzweigte lamellenartige Auffaltungen, die wechselseitig ineinandergreifen. Nach Einfließen von Eizelle und Dotterzellen in den Uterus verstreichen die Auffaltungen zu einer glatten inneren Begrenzung des Lumens. Anschließend werden zahlreiche Schalentropfen aus den Vesikeln der Dotterzellen freigesetzt. Sie fließen an der dünnen Sekretschicht der Uteruszellen, die die Innenseite des Uterus bedeckt, zu einer Eihülle ineinander. Bei geringen Mengen Uterussekret entsteht keine geschlossen einheitliche Schicht. Aus der anfänglich dünnen Eihülle geht durch Aufnahme weiterer Schalentropfen und anschließende Sklerotisierung die braune Eikapsel hervor.
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Bunke, D. Ultrastruktur-Untersuchungen zur Eischalenbildung bei Microdalyellia fairchildi (Turbellaria). Zoomorphology 101, 61–70 (1982). https://doi.org/10.1007/BF00312030
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DOI: https://doi.org/10.1007/BF00312030