The Functional Morphology and Adaptations of the Epididymis in a Testicndid Mammal, The Rufous Sengi (<i>Elephantulus rufescens</i>).

Abstract

Sengis are testicondid African mammals that constitute Order Macroscelidae. The epididymal morphology in the rufous sengis (Elephantulus rufescens) was studied with focus on features and adaptations that make it suitable for sperm maturation and storage in this testicondid mammal. The three topographic regions were distinct with the caput and cauda epididymis placed far apart, connected by a slender corpus. The caput occurred as a longitudinal mass on the dorsolateral border of the testis while the Cauda, pear-shaped mass, was laterally placed between the rectum and the pelvic urethra. The epididymal epithelium comprised principal and basal cells; the former exhibiting granules and apical blebbing in the caput. The lumen of the cauda was densely packed with spermatozoa that are occasionally wrapped by amorphous dark masses, and its principal cells had numerous vacuoles. This study demonstrates that beside merocrine secretion, principal cells of sengi’s caput also exhibit apocrine secretion as shown by apical blebs. The blebs are shed off plausibly as a means of delivering epididymosomes to the lumen, which in turn transfer epididymis-secreted proteins to the spermatozoa. Additionally, the study has shown that the cauda epididymis descends to a site probably cooler than the core body temperature for optimal sperm storage, with the vacuoles indicating its involvement in fluid re-absorption and phagocytosis.