Summary
The midgut epithelial cells of the eutardigrade Isohypsibius augusti are organized into a convoluted monolayer. Only a single cell type could be distinguished although this cell type displayed considerable morphological variation. The midgut begins with crescent-shaped cells. More distally the cells are of variable height depending on the stored amount of nutritional material. No regenerative cells are present. Adjoining cells are held together by apical zonulae continuae. All the cells are characterized by a striated border, some basal infoldings, cytosis vesicles, numerous mitochondria, and abundant rough endoplasmic reticulum. Dictyosomes occur in small numbers. Ovoid or spherical inclusions (spherites), often concentrically laminated, are common. The cells, especially those along the middle part of the gut, are filled with large amounts of nutritional storage which includes polysaccharide material. The possible functions of the midgut in Tardigrada are discussed.
Zusammenfassung
Das einschichtige, stark gewundene Mitteldarmepithel des Eutardigraden Isohypsibius augusti besteht aus nur einem Zelltyp. Der Mitteldarm beginnt mit halbmondförmigen Zellen; die Höhe der sich anschlie-ßenden Zellen schwankt je nach der Menge der eingelagerten Nahrungsreserven. Regenerative Zellen fehlen. Benachbarte Zellen sind apikal durch Zonulae continuae verbunden. Alle Mitteldarmzellen zeichnen sich durch einen apikalen Mikrovillisaum, Cytosevesikel, zahlreiche Mitochondrien und viel rauhes endoplasmatisches Retikulum aus. Dictyosomen sind nicht allzu häufig. Verbreitet sind ovoide oder runde, oft konzentrisch geschichtete Einschlüsse (Spherite). Besonders die Zellen des mittleren Darmabschnittes können mit großen Mengen von Nahrungsreserven gefüllt sein, die zum Teil Polysaccharide enthalten. Mögliche Funktionen des Mitteldarms der Tardigraden werden diskutiert.
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I am indebted to Mr. B. Fink, Münster, for correction of the English manuscript.
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Greven, H. Some ultrastructural observations on the midgut epithelium of Isohypsibius augusti (Murray, 1907) (Eutardigrada). Cell Tissue Res. 166, 339–351 (1976). https://doi.org/10.1007/BF00220130
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DOI: https://doi.org/10.1007/BF00220130