SCANNING ELECTRON-MICROSCOPIC STUDY OF THE CYTOPLASMIC TUBULES IN LAMPREY CHLORIDE CELLS

The three-dimensional architecture of the cytoplasmic tubules (CT) of chloride cells in the lamprey (Lampetra japonica) gill was examined by scanning electron microscopy using an osmium maceration technique. Th e CT were classified into two types according to their three-dimension al organization and intracellular location: one type forming a fine ne twork associated with abundant mitochondria in the peripheral cytoplas m; and the second type forming densely packed bundles of straight tubu les in the perinuclear cytoplasm. Both types of CT were often continuo us with each other, showing that they form a continuous tubular system in the cytoplasm. The network-type CT may be involved in ion excretio n, whereas the bundle type may serve as a membrane reservoir.