Regional Histology and Histochemistry of the Ductus Epididymis in the Rhesus Monkey (Macaca mulatta)1

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Abstract
Examination of epididymides from 6 sexually mature male rhesus monkeys revealed epididymal epithelial and stereocilial height was maximal in the caput region and minimal at the cauda. Luminal diameter was just the reverse. Strong acid phosphatase activity was localized principally in the supranuclear area of the columnar cells in the distal caput and corpus epithelia. Stereocilia were practically devoid of this activity. Moderate alkaline phosphatase activity was localized in the basal cells of the corpus and proximal cauda epididymidis, while activity in the principal cells was slight. Luminal contents of ductuli efferentes and epididymis had much more alkaline phosphatase activity than tissues. PAS positive materials were most evident in the apical epithelium of the ductuli efferentes and distal caput and in the luminal contents beyond the proximal caput. Location of the cytoplasmic droplet on the sperm midpiece changed from proximal to distal between distal caput and proximal corpus. Progressive sperm motility changed dramatically between distal corpus (15%) and proximal cauda (75%). It was hypothesized that some rhesus sperm within the distal corpus (second portion of the middle segment) would have acquired fertilizing ability.