Ultrastructural changes of the midgut epithelium in Isohypsibius granulifer granulifer Thulin, 1928 (Tardigrada: Eutardigrada) during oogenesis |
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Authors: | Magdalena M Rost-Roszkowska Izabela Poprawa Maria Wójtowicz ?ukasz Kaczmarek |
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Institution: | (1) Department of Animal Histology and Embryology, University of Silesia, Bankowa 9, 40-007 Katowice, Poland;(2) Department of Animal Taxonomy and Ecology, A. Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland |
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Abstract: | The midgut epithelium of Isohypsibius granulifer granulifer (Eutardigrada) is composed of columnar digestive cells. At its anterior end, a group of cells with cytoplasm which differs
from the cytoplasm of digestive cells is present. Probably, those cells respond to crescent-like cells (midgut regenerative
cells) described for some tardigrade species. Their mitotic divisions have not been observed. We analyzed the ultrastructure
of midgut digestive cells in relation to five different stages of oogenesis (previtellogenesis, beginning of the vitellogenesis,
vitellogenesis—early choriogenesis, vitellogenesis—middle choriogenesis, late choriogenesis). In the midgut epithelium cells,
the gradual accumulation of glycogen granules, lipid droplets and structures of varying electron density occurs. During vitellogenesis
and choriogenesis, in the cytoplasm of midgut cells we observed the increasing number of organelles which are responsible
for the intensive synthesis of lipids, proteins and saccharides such as cisterns of endoplasmic reticulum and Golgi complexes.
At the end of oogenesis, autophagy also intensifies in midgut epithelial cells, which is probably caused by the great amount
of reserve material. Midgut epithelium of analyzed species takes part in the yolk precursor synthesis. |
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