Ultrastructure of the tubular nephron of Testudo graeca (Chelonia). A comparison between hibernating and non-hibernating animals

Abstract

The tubular nephron of hibernating and nonhibernating specimens of Testudo graeca (Chelonia) was studied by means of conventional light and electron microscopy and histochemistry. The tubular nephron was composed of proximal, intermediate, distal and collecting tubules in both hibernating and nonhibernating animals. The cells of the proximal tubule showed long microvilli, cytoplasmic vacuoles, a developed endoplasmic reticulum and abundant mitochondria. Fat droplets were also observed. The intermediate segment was lined by ciliated and nonciliated cells. The lining cells of the distal tubule presented few microvilli, abundant dense mitochondria and clear vesicles of mucous appearance in the terminal portion. Collecting ducts are composed of mucous and non-mucous cells. Mucous cells presented strong reaction to the histochemical techniques detecting sialoand sulpho-mucins. During hibernation, a progressive vacuolar degeneration of the endoplasmic reticulum was observed in al1 the segments of tubular nephron, which may be caused by a massive intake of extracellular water into the cell.