Electron microscope study on the bat testicular interstitial cell with special reference to the cytoplasmic crystalloid.

The testicular interstitial cell of the bat, Myotis schreibersi (Temmink), captured late in August was electron microscopically investigated. The cytoplasm of Myotis interstitial cells is packed by strikingly numerous mitochondria with many electron dense small matrix granules, endoplasmic reticulum and variable numbers of osmiophilic lipid droplets. The Myotis interstitial cell is characterized by alternate development of the SER and RER: In some Leydig cells the major part of the cytoplasm is packed by tubular SER, whereas in others this apparently is replaced by abundant free ribosomes containing sparse cisternae of the RER. These changes in the amounts of ser and RER are likely reversible and probably reflect functional alterations of Leydig cells of the bat, a hibernator. The Myotis interstitial cell possesses small cytoplasmic crystalloids composed of regularly oriented, compressed tubules, 20-28 m mu thick, which are continuous to the tubular SER (SER derived crystalloids). Type I and type II crystalloids are classified, which show, in suitable planes of section, honeycomb-like and fabric-like patterns, respectively. The Myotis Leydig cell extends cytoplasmic processes of irregular shape and long microvilli, the latter often conglomerates on the cell body or cytoplasmic processes. The entire surface of the cell including the processes is completely surrounded by a basal lamina.