Elektronenmikroskopische Beobachtungen am Saccus Vasculosus des Kugelfisches, Spheroides Niphobles

Abstract

The saccus vasculosus of the globefish, Spheroides niphobles, was studied by means of electron microscopy.
The cytoplasm of the coronet cells is characterized by an elaborate network of tubular or cisternal agranular endoplasmic reticulum extending from its basal region to the apical cytoplasmic protrusion. Near the cytoplasmalemma in the apical cytoplasmic protrusion, from the upper part of which spoon-like globules with a stalk project radially into the saccus cavity, are scatterd also small dense granules with a distinct limiting membrane about 500Å in diameter. The cilium in each stalk is a hollow cylinder which consists of nine pairs of peripheral tubules, lacking the central ones. The cytoplasm of the globules is occupied by a large number of tubules and vacuoles of various sizes, many of which contain dense granules about 400Å in diameter. Though not very often, openings of these tubules and vacuoles into the saccus cavity can be observed. The most striking feature of the globules is that all the membrane-limited structures including the plasmalemma possess at their cytoplasmic surface a pelage about 300Å in thickness which consists of cloud-like material. Its histochemical property is discussed in connection with the possible function of the coronet cell. Within the saccus wall can occasionally be seen bundles of unmyelinated nerve processes. There are distinguished two types of nerve endings: One is characterized by a number of small vesicles with and without dense cores about 500Å in diameter while the other is, on the average, of smaller caliber and contains only a few empty vacuoles and a number of scattered glycogen particles. The basal region of the coronet cells does not reach the basement membrane of capillaries, but both structures are separeted by a cytoplasmic layer of the supporting cells which encloses the coronet cells.