The Morphology and Morphometry of the male reproductive system of Rufous Sengi (Elephantulus Rufescens).

Abstract

The Morphology of the male reproductive system of rufous sengi was studied using light and electron microscopy while the testicular morphometry was studied using stereological techniques. The system consisted of cylindrical-shaped testes, genital ducts, accessory sex glands and the penis. The testes were intra-abdominal, located just caudal to the kidneys and comprised of a parenchyma bound by tunica albuginea. The parenchyma was composed of the seminiferous tubules and the interstitial tissue; the former being more predominant than the later and exhibiting complete spermatogenesis. The interstitial tissue occurred either between the seminiferous tubules, mainly in relatively larger spaces formed when three or four seminiferous tubules approximate one another or beneath the tunica albuginea. The Leydig cells were generally polyhedral with irregular nuclei and had numerous lipid droplets within their cytoplasm but, in cases where the interstitial tissue made extensions into narrow spaces between adjoining seminiferous tubules, the Leydig cells therein were elongate with rod-shaped nuclei. The testicular arteries branched off from renal arteries and ran cando-laterally to

the testis without convolutions or intimate association with the vein. The testicular veins also followed a straight course, without pampiniform plexuses. These animals had separate right and left caudal vena cavae which received ipsilateral testicular and renal veins. After receiving the renal veins, the left caudal vena cava crossed to the right side to join the right one to form a common caudal vena cava which then extended cranially up to the right atrium.

The genital ducts comprised of the rete testis, efferent ductules, epididymis, ductus deferens and the urethra. The rete testis was made up of interconnecting channels located outside the testicular parenchyma while the efferent ductules connected the rete testis to the caput epididymis. The epididymis consisted of a highly coiled duct organized into three topographic regions; the caput, corpus and cauda epididymis. The caput epididymis was applied on dorso-Iateral border, extending from cranial to the caudal pole of the testis. The corpus epididymis extended caudally from the caput to a position between the pelvic urethra and the rectum where it joined the cauda epididymis. The cauda epididymis was organized into a pear-shaped mass, located in a somewhat lateral position between the rectum and the pelvic urethra. The caput and corpus epididymis were lined by a tall pseudostratified columnar epithelium while the cauda epididymis was lined by cuboidal or low columnar epithelium. The ductus deferens was short, connecting the cauda epididymis to the pelvic urethra. The urethra consisted of two parts; the pelvic and the penile urethra. The pelvic urethra, surrounded by a thick muscular coat, extended from the neck of the urinary bladder to the bulb of the penis and received the ductus deferens, uterus masculinus and the ducts of the accessory sex glands. The

penile urethra extended from the bulb to the tip of the penis. The accessory sex glands consisted of the prostate and bulbourethral glands but without vesicular glands. The prostate gland was made up of several paired lobes organized into two groups; the cranial and the caudal group of lobes, also referred to as the cranial and the caudal prostates respectively. The cranial

prostate consisted of lobes organized around the neck of urinary bladder and included the ventral, latero-dorsal and the medio-dorsallobes. The caudal prostate consisted of a single pair of lobes located dorsal to the pelvic urethra. The bulbourethral gland consisted of a pair of medio-Iaterally flattened glands found laterally at about the junction brtween the pelvic urethra and the bulb of penis. The mean reference volume of the sengi testis was 0.089 ± 0.003 ern", 98.3% of which was constituted by the parenchyma and the rest being contributed by the capsule. The seminiferous tubules occupied 90.94% of the testicular parenchyma, while the interstitial tissue, on the other hand, occupied about 9.07%. Out of this total interstitial tissue volume, 7.6% was contributed by the subcapsular interstitial tissue. The morphology of the male reproductive system of the sengi and the pattern of testicular blood vessels was generally similar to that of the African elephant and the rock hyrax, supporting the existence of close phylogenetic relationships between these animals as earlier suggested. Additionally, the pattern of testicular blood vessels suggest that they play no role in testicular thermoregulation. The separate left and right caudal vena cava is most likely due to retention of embryonic pattern to adulthood. The morphometric data on the testis confirmed, with quantification, that the parenchyma of sengi's testis is predominated by the seminiferous tubules with little interstitial tissue.