The opisthonephric kidney of the sea lamprey of the Great Lakes, Petromyzon marinus L. V. The archinephric duct.

Abstract

AbstractThe 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.The archinephric duct of the adult lamprey is morphologically distinct from that of the ammocoete and appears to be involved in the production of mucus and in the expulsion of urine by contraction of its muscular wall. Its stratified epithelium is divided into basal, intermediate, and superficial cells and intracellular PAS‐positive granules increase progressively in number from the basal to surface cells. The superficial cells can be further divided into four types and a progression of cell types from the base to the surface of the epithelium is suggested. A thick electron‐dense apical cell coat, apical vesicles, and mucous granules probably account for the intense staining of the surface with PAS. These features indicate that a closer structural relationship exists between the lamprey archinephric duct and the excretory ducts of other lower vertebrates than with the ureter of mammals.