摘要：

The archinephric duct of ammocoetes consists of two morphologically distinct regions. An anterior and posterior region are lined by a columnar epithelium that often possesses wide, lateral intercellular spaces. Some cells in the anterior region are characterized by an electron-dense apical cell coat and dense apical vesicles, while others resemble cells of the collecting tubule. In the posterior region all cells possess large accumulations of glycogen, mitochondria, and smooth endoplasmic reticulum. There is reason to believe that transport of ions and fluids may occur in the duct and, although some morphological evidence indicates a role in protein absorption, these cells do not appear to be specialized for this function.

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