Topography of Ca2+-sequestering endoplasmic reticulum in photoreceptors and pigmented glial cells in the compound eye of the honeybee drone |
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Authors: | O. Baumann B. Walz |
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Affiliation: | (1) Institut für Zoologie, Universität Regensburg, Regensburg, Germany;(2) Institut für Zoologie, Universität Regensburg, Universitätsstr. 31, Postfach 397, D-8400 Regensburg, Germany |
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Abstract: | Summary The endoplasmic reticulum (ER) in the photoreceptors of the honeybee drone, Apis mellifera, is highly differentiated and morphologically more complex than suggested by previous studies. In addition to the prominent voluminous submicrovillar cisternae we describe a submitochondrial ER. It separates the mitochondria-containing periphery from the core of the cell. The cell core contains many fenestrated ER cisternae that are horizontally and periodically arranged. We show that all parts of the ER, except for a tubulovesicular portion but including the nuclear envelope, are continuous; all parts appear to accumulate Ca2+ actively and with high affinity. Our results confirm previous suggestions that the submicrovillar ER is the major intracellular Ca2+ -store in the photoreceptors. The submitochondrial ER is thought to participate in Ca2+-regulation in the mitochondrial microenvironment. Moreover, we describe for the first time an extensive, morphologically complex Ca2+-sequestering ER in the pigmented glial cells; it might participate in the regulation of the glycogen metabolism. |
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Keywords: | Photoreceptor cells Glia-like cells Endoplasmic reticulum, rough Endoplasmic reticulum, smooth Calcium ions Apis mellifera (Insecta) |
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