ASPECTS OF SPERM PRODUCTION IN SOME EAST AFRICAN MAMMALS T. D. GLOVER Unit of Reproductive Biology, University of Liverpool, P.O. Box 147, Liverpool L69 3BX (Received 1st September 1972) Summary. A comparison of certain features of the testis and epididymis has been made in five species of East African mammals, two of which, the rock hyrax and elephant, have abdominally situated testes. The artery to the testes was straight in the species with abdomi- nally situated testes and there was no pampiniform plexus while in the species with scrotal testes, it was coiled in the region of the plexus. It is suggested that where the testicular artery is coiled, the testes should be regarded as basically scrotal, even if they are usually found in the abdomen post mortem. A striking increase in blood flow in the testis of the rock hyrax during sexual activity suggests that the simpler arterial pattern of the testis in testicond mammals allows a greater variation in blood flow than the more complicated arterial design associated with scrotal testes. Characteristic signs of sperm maturation occur in the epididymis of testicond mammals in contrast to the situation in artificial cryptor- chidism, where normal epididymal function is completely disrupted. It is suggested that epididymal function, as well as spermatogenesis, has become modified during evolution. Evidence is given that a need for prolonged survival of spermatozoa in the mesonephric duct might have been an important primary factor in the caudal migration of gonads into a scrotum. INTRODUCTION In this paper, reference is made mainly to the testis and epididymal contents of the giraffe, Giraffa, eland, Taurotragus, steinbok, Raphicerus, jumping hare, Pedetes, rock hyrax or dassie, Procavia and Heterohyrax, and elephant, Loxodonta, because examples of all these genera are found in equatorial Africa and thus have several features of environment in common. In the first four genera, the testes are situated in a scrotum. In the hyrax and the elephant, they are permanently and normally in the abdomen (mammalian testiconda). The jumping hare has a scrotal pouch but the testes have been described as being abdominal (Coe, 1969). In mammals in which the testes and epididymides are in a scrotum, the production of spermatozoa comprises spermacytogenesis, involving cell d 45 Downloaded from Bioscientifica.com at 09/29/2021 09:58:43AM via free access 46 T. D. Glover division, and spermateliosis, involving no cell division. The process of sperm maturation, therefore, begins in the testis but is continued in the epididymis long after the spermatozoa leave the testis. It is well known that in scrotal mammals, spermatogenic activity of the testis is highly susceptible to elevated temperature. It has also been shown that maturation and survival of sper¬ matozoa in the epididymis is extremely sensitive to increased temperature. In artificial cryptorchidism, for instance, epididymal spermatozoa show a rapid loss of function and soon degenerate (Glover, 1960; Cummins & Glover, 1970). In the mammalian testiconda, therefore, the question arises of how spermato¬ genesis proceeds at abdominal temperatures, and how spermatozoa can mature and survive in an epididymis that is permanently in the abdomen. Harrison (1949) pointed out the unusual arterial architecture of scrotally situated testes, and there is evidence to suggest that this might be a disadvantage to the organs in adapting to increased temperature (Setchell & Waites, 1970). For this reason, the course and distribution of the testicular artery was examined in the present work, particular attention being paid to animals with abdominal testes. Certain distinct changes are known to typify sperm maturation in the epididymis, and in mammals with scrotal testes, the tail of the epididymis is recognized as an area which is conducive to prolonged survival of mature spermatozoa. Although reference has been made to these events in the hyrax and the elephant (Glover, 1968; Glover & Sale, 1968), there is little information about them in African mammals generally. It was, therefore, decided to examine spermatozoa from different levels of the epididymis in the different species. MATERIALS AND METHODS Material was collected from two eland bulls, two steinbok, three giraffe, eight rock hyraxes and three elephants in Kenya. Further investigations were made on rock hyrax from the Transvaal, South Africa, and on one elephant shot on the banks of the Crocodile River bordering the Kruger National Park, near Komatipoort. Examination of the testicular artery was carried out in each case according to the method of Harrison (1951), using an injection of radio-opaque material and the subsequent production of an arteriograph. Micropaque (barium sulphate, 100% w/v, Damancy & Co., Ltd) was used for direct injection into the testicular artery of larger species and into the thoracic or abdominal aorta of smaller species. The injection was always made slowly, either by using a sim¬ ple record syringe or by gravity feed, according to circumstances. The giraffe was the only species in which it was found necessary to flush out the artery with saline before introducing the injection fluid. The particle size of the Micropaque is such that it does not pass through capillaries and thus it only fills the arterial side of the vasculature. After injection, the testes were removed and stored at a temperature of 0° C, or lower, before X-rays were taken. For a thorough examination of material, it is difficult to perform all the required procedures on the same animal. Hence, spermatozoa were usually Downloaded from Bioscientifica.com at 09/29/2021 09:58:43AM via free access Sperm production in some East African mammals 47 taken from separate fresh specimens which were dissected out and examined as soon as possible after the death of the animal. Spermatozoa were collected by incising the epididymis at different levels (Text-fig. 1) and gently squeezing out the spermatozoa onto a microscope slide. The first sample was quickly examined under the microscope for motility. If the spermatozoa were immotile, the sample was slightly diluted with fructose Ringer phosphate solution (Mann, 1964). No attempt was made to quantify motility; a subjective assessment of Text-fig. 1. Homologous areas of the epididymis in a scrotal mammal (left) and a testicond mammal (right) from which spermatozoa were withdrawn for examination. 1 = caput epididymidis; 2 = cauda epididymidis. 'good', 'medium' or 'nil' was made. When this examination was complete, a further sample from the same area was taken, mixed with one drop of aqueous nigrosin eosin on a microscope slide, smeared onto the same slide and a dup¬ licate smear made on another slide from the residual spermatozoa-stain mixture on the cover slip. Each was allowed to dry in air before being mounted in DPX. Later, 100 spermatozoa were counted on each slide for an estimate of mor¬ phological features. Further smears were made for staining with Papanicolaou's stain (Papanicolaou, 1942) for confirmation of the morphological picture. Downloaded from Bioscientifica.com at 09/29/2021 09:58:43AM via free access 48 T. D. Glover Since it was not possible to test the fertilizing capacity of the spermatozoa, a morphological indicator of sperm maturation was used in addition to the observation ofmotility. The criterion taken was the migration of the cytoplasmic droplet to the end of the mid-piece (Lagerlöf, 1934; Merton, 1939). Contraction of the acrosome round the nucleus as seen in maturing rabbit spermatozoa (Bedford, 1965) was unreliable as a guide to sperm maturation in this instance because conditions were conducive to membrane damage and any abnormal swelling of the acrosomes would make quantitative interpretations difficult. Measurements of sperm size were made with the use of an ordinary eyepiece micrometer gauge. Text-figure 1 illustrates the levels of the mesonephric duct from which sperma¬ tozoa were withdrawn in both scrotal and testicond species. The levels in each type of mammal are based on homologues suggested earlier (see Glover, 1968; Glover & Sale, 1968). RESULTS The course and distribution of the testicular artery In the eland and steinbok, the testicular artery forms a helix in the region of the pampiniform plexus and runs onto the surface of the testis underneath the tunica albugínea. Here, it divides dichotomously into two main arteries, the branches of which run into and supply the testis parenchyma. This arterial pattern is essentially the same as that in domesticated ruminants and is again to be seen in the testis of the giraffe. In the giraffe, however, the artery is more convoluted in the region of the pampiniform plexus and the coils extend onto the surface of the testis (PI. 1, Fig. 1) before the artery continues in its course under the tunica albugínea. In the jumping hare, the testicular artery is also coiled before reaching the testis. There is a distinct pampiniform plexus of veins and the artery courses tortuously under the tunica albugínea in a similar but more exaggerated fashion than that of the rat (PI. 1, Fig. 2). In contrast to these patterns, the testicular artery of the hyrax is straight (Harrison, 1958), although it may show a slight kink in some animals (PI. 1, Fig. 3). The artery does not run far on the surface of the testis but divides into two major arteries whose branches enter the testis directly from one side only. The left testicular artery arises from the inferior renal artery, there being three arteries to each kidney. The male rock hyrax is a seasonal breeder, and specimens were taken from both sexually active and sexually quiescent animals (Glover & Sale, 1968). Differences in the size of the testes between these two are often quite remarkable (Millar & Glover, 1970) and it was observed that, in sexually active animals, the testicular artery and its branches were much better filled with Micropaque than in sexually quiescent animals.