Seasonal changes in fine structure of the ductuli efferentes of the ground squirrel, Citellus lateralis (Say).

The morphological changes that the ductuli efferentes undergo during the seasonal breeding cycle of the ground squirrel Citellus lateralis were examined by means of electron microscopy. At the time of spermatogenetic activity the epithelium of the ductuli was composed of highly differentiated principal and ciliated cells. Distinctive cytological features of these cells during this period were the presence of a heterogeneous collection of numerous membrane-bound granules in principal cells and large accumulations of glycogen in ciliated cells. Structurally these cells were specialized for movement of luminal contents and its modification by absorption and possible secretion. With the onset of testicular regression, profound changes occurred in both cell types. Initially the lumen of the ductuli became occluded by masses of apical cytoplasm protruded from principal and ciliated cells as well as by degenerating cells which had been sloughed from the epithelium. This leads eventually, by the time of complete testicular regression, to reduced ductuli containing cells smaller in size with fewer organelles than those present during the period of spermatogenesis. The membrane-bound granules in principal cells and the accretions of glycogen in ciliated cells had now virtually disappeared. There was, however, a dramatic increase in dense inclusions representing deposits of lipofuchsin. As yet the cellular mechanisms controlling and effecting these dramatic changes in morphological appearance are unknown.