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. The CT were classified into two types according to their three-dimensional organization and intracellular location: one type forming a fine network associated with abundant mitochondria in the peripheral cytoplasm; and the second type forming densely packed bundles of straight tubules in the perinuclear cytoplasm. Both types of CT were often continuous with each other, showing that they form a continuous tubular system in the cytoplasm. The network-type CT may be involved in ion excretion, whereas the bundle type may serve as a membrane reservoir.