Kikuchi S
Cell Tissue Res. 1983;229(2):253-68. doi: 10.1007/BF00214974.
Two kinds of epithelial cells, dark and light types, are alternately arranged in the gill of Daphnia magna. The dark cell has numerous mitochondria and an elaborate tubular system containing two kinds of cytoplasmic tubules, small about 70 nm in diameter, and large about 130 nm in diameter. The former occur in bundles and seem to be smooth-surfaced endoplasmic reticulum. The latter, lined with a ridged surface coat and frequently open at the lateral and basal cell membrane, are regarded as extensions of the cell membrane. The atypical cell membrane of the dark cell is modified by repeated subunits of a cytoplasmic coat on the inner leaflet of the unit membrane. The light cell exhibits a high degree of basal infoldings of the cell membrane, which represent a magnification of the surface area of the cell. Large mitochondria between the infoldings often come into intimate association with the infolded cell membrane to form a regular array of parallel mitochondria interposed with the double cell membranes. The results suggest that at least the dark epithelial cells play an important role in the osmoregulation of this animal.
大型溞鳃中的两种上皮细胞，即暗细胞和亮细胞交替排列。暗细胞有大量线粒体和一个复杂的管状系统，该系统包含两种细胞质小管，一种直径约70纳米，较小；另一种直径约130纳米，较大。前者成束出现，似乎是光滑表面的内质网。后者内衬有带脊的表面涂层，且常在细胞侧面和基底细胞膜处开口，被认为是细胞膜的延伸。暗细胞的非典型细胞膜在单位膜内小叶上由细胞质涂层的重复亚基修饰。亮细胞表现出细胞膜高度的基底内褶，这代表细胞表面积的扩大。内褶之间的大型线粒体常与内褶的细胞膜紧密相连，形成一系列由双层细胞膜夹着的规则排列的平行线粒体。结果表明，至少暗上皮细胞在这种动物的渗透调节中起重要作用。
