ULTRASTRUCTURE OF THE EPITHELIUM THAT LINES THE DUCTULI EFFERENTES INDOMESTIC EQUIDAE, WITH PARTICULAR REFERENCE TO SPERMATOPHAGY

The epithelium that lines the ductuli efferentes in the horse, donkey and mule has been examined by electron microscopy. The epithelium cons ists of columnar ciliated and non-ciliated cells. Lymphocytes and macr ophages are also present, together with cells that are rich in lipofus cin. These 'lipofuscin-rich' cells are a peculiar feature of the excur rent ducts of Equidae and are characterized by a large number of highl y heterogeneous residual bodies. The general morphology of the epithel ium and, in particular, of the non-ciliated cells implies that the epi thelium is involved in the absorption and digestion of luminal fluids. This morphology includes a complex endocytotic apparatus as well as a large and heterogeneous population of lysosomal structures within the cytoplasmic domain. Of particular interest is the unusual presence of peroxisomes. In the Equidae, the cells that compose the epithelial la yer appear to net directly on the germinal cells, via the process of s permatophagy. The presence of peroxisomes in nonciliated cells has bee n implicated in endocytotic and spermatophagic activities, and peroxis omes may be involved in the oxidation and elimination of toxic peroxid es.