- 期刊
Fine Structure of the Midgut Epithelium of Atelura formicaria (Hexapoda: Zygentoma: Ateluridae), with Special Reference to Its Regeneration and Degeneration
並列摘要
Atelura formicaria belongs to a basal hexapod group, the Zygentoma. Its midgut epithelium is composed of epithelial cells, which are responsible for digestion, secretion, and absorption, and regenerative cells, which form regenerative nests. The midgut epithelium ultrastructure was compared to that described for other zygentoman groups, the Lepismatidae, and the Archaeognatha, a group closely related to the Zygentoma. Among regenerative cells, we distinguished midgut stem cells (resting regenerative cells), which are able to proliferate and differentiate, and differentiating regenerative cells. Just before mitotic division in the cytoplasm of stem cells, many cisterns of endoplasmic reticulum and electron-dense granules appear. During mitosis, the electron-dense granules are still present, but are not visible in the resting regenerative cells. A morphological sign of midgut stem cell differentiation is the accumulation of mitochondria just above the nuclei. They gradually assume characteristic features of epithelial cells during elongation toward the midgut lumen. Proliferation and differentiation of regenerative cells are caused by processes of degeneration (apoptosis and necrosis), which intensively occur in the midgut epithelium of A. formicaria.