Testicular atrophy in captive gorillas (Gorilla g. gorilla)

J. Zool., Lond. (1980) 191, 315-322

Testicular atrophy in captive gorillas (Gorilla g. gorilla) A . F . D I X S O NH, . D. M . M O O R EA N D W. V . HOLT Wellcome Laboratories of Comparative Physiology, Institute of Zoology, Zoological Society of London, Regent’s Park, London (Accepted 9 October 1979) (with 3 plates in the text) Testes were obtained at post mortem from three Western lowland gorillas, two Bornean orang-utans and one Chimpanzee. All specimens were adults which had died in captivity. Histological examination revealed that two gorillas exhibited complete degeneration of the seminiferous tubules and that the testes contained large amounts of interstitial tissue. Some, less obvious, signs of degeneration were noted in the third specimen but poor preservation of the material hampered interpretation of these features. The testes of the Orang-utans and Chimpanzee were structurally normal. Testicular atrophy in captive gorillas may be more common than is generally realized and there is a need for research on fertility and reproductive endocrinology of male specimens. At the moment it is not possible to identify the causes of testicular dysfunction in captive gorillas.

Contents

.. . . . Introduction Materials and methods . . . Results .. . . . . . Gorillas .. . . . Orang-utan and Chimpanzee Discussion . . . . . . . Summary . . .. . . . References . . .. . . .

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Introduction At the present time there are approximately 460 gorillas in world zoos and other institutions (Olney, 1978). Since this species is endangered in its natural habitat, factors which affect reproduction in the captive population are of particular interest. In the male gorilla there have been reports that the adults undergo testicular atrophy in captivity (Koch, 1937; McKenney, Traum & Bonestell, 1944; Clarke, 1948; Steiner et al., 1955; Inoue & Hayama, 1961-62; Antonius et al., 1971). It is not known whether testicular atrophy is common among captive gorillas or what factors cause the dysfunction. This may be due partly to the general lack of information concerning testicular morphology in great apes, particularly the gorilla, since only four specimens have been examined histologically. In an attempt to clarify this situation we have studied the reproductive status of a further three adult male gorillas which died in captivity. Studies were conducted using both the light and electron microscope. To provide comparative information on testicular morphology, tissues from two other great apes, the Orang-utan and Chimpanzee, were also examined. 315 0022-5460/80/0703 15

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1980 The Zoological Society of London

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Materials and methods Reproductive organs were obtained at post mortem from three male Western lowland gorillas, two male Bornean orang-utans and one male Chimpanzee. All the specimens were adults which had died in captivity. Details of their ages, body weights, breeding histories and causes of death are given in Table I. T A B L E1 Details of ihe six aduli male great upes studied

Species and name

Date and place of death

Cause of death

Approximate Weight age (years) (kg)

Number of Tissues offspring examined

Gorilla g. gorilla “Oban” Y.R.P.R.C.

January 1976 Gorilla g. gorilla “Jojo” Chester Zoo March 1978 Gorilla g . gorilla “Guy” Z.S.L. June 1978 Pongo p . pygmaeus

“Oscar” Pongo p . pygmaeus “Boy” Parz troglodytes ‘‘Freddie.’

J. W.P.T. July 1973 Z.S.L. March 1976 Z.S.L. October 1977

Gastro-enteritis

12

79

0

Testes

Pneumonia

18

ND

0

Testes

Anaesthesia-failed to recover after dental surgery Ulcerative colitis

33

240

0

14

85

2

Entire genital tract Testes

Hepatic failure, causes unknown Euthanasia

14

100

8

Testes

16

ND

ND

Testes

Y.R.P.R.C. : Yerkes Regional Primate Research Center Z.S.L. : Zoological Society of London J.W.P.T. : Jersey Wildlife Preservation Trust ND : No data

Testes were prepared for routine histology and stained with haematoxylin and eosin for examination in the light microscope. Additional material was prepared for electron microscopy by immersion in PFG-cacodylate fixative (It0 & Karnovsky, 1968) and post fixation in 1 osmium tetroxide in 3 % potassium ferrocyanide (Dym & Romrell, 1975). The tissue was then dehydrated and embedded in Epon 812. Ultrathin sections were stained with uranyl acetate and lead acetate and examined in an A.E.I. 6B electron microscope at 60 kV.

Results

Gorillas The genital tract of “Guy” was removed a few hours after death. Both testes were fully descended, the left one being associated with a scrota1 hernia. They were extremely small, measuring 27 x 18 mm (right) and 28 x 19 mm (left). The corresponding weights including the epididymides were 6.85 g and 4.4g respectively. Despite a careful examination it was not possible to locate either the seminal vesicles or prostate. Sections of the testes exhibited a diffuse nodular appearance (Plate I(a)) and microscopic examination revealed that the seminiferous tubules were totally degenerate and fibrosed.

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PLATE I. (a) L.S. of right testis of the gorilla “Guy” ( x 5) to show the diffuse nodular appearance of the tissues. (b) A light micrograph of the gorilla testis (“Guy”). The seminiferous tubules are degenerate and fibrosed and there is an extensive stroma of interstitial cells ( x 160).

PLATE11. (a) An electron micrograph of gorilla testis(“Guy”). Interstitial cells contain dense lysosomal inclusions (arrowed) and membrane bound lipid droplets (L). The cytoplasmic membrane is disorganized ( x 8800). (b) A light micrograph of the caput epididymis of the gorilla (“Guy”). The epithelial cells appear squat and contain many dense lysosomes. Some differentiation of the epithelium is apparent, however, as principal and apical cells (arrowed) are present. The epididymal lumen is devoid of spermatozoa and contains lipid particles ( x 256).

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None of the stages of spermatogenesis were identifiable. The basement membranes of the tubules were not discernible although numerous slightly paler staining ovoid areas which may have represented the remnants of seminiferous tubules were present, along with a stroma of unidentified interstitial cells and fibrosed tissue (Plate I(b)). Fine structural observations of the testes clearly showed a degenerate condition in which the geminal epithelium and functional Leydig cells were absent (Plate II(a)). There were two small interstitial cell adenomas in the left testis, further details of which are given elsewhere (Jones et al., in press). The epididymides of “Guy” were atrophic and contained shrunken epithelial cells (Plate II(b)). These had few microvilli, a disorganized Golgi complex and contained many mitochondria and dense lysosomal bodies. Nevertheless, the epididymal epithelium had differentiated at some stage since several distinct cell types were present. The testes from the second male gorilla, “Jojo”, were histologically similar to those from “Guy”. The seminiferous tubules were completely degenerate and there was an extensive stroma of interstitial cells and fibroscd tissue. No measurements of the testes were made at post mortem, but they were noted to be extremely small and haemorrhagic (Ellis, pers. comm.). Marked dilatation of the blood vessels was apparent in sections of both testes. Observations of testicular structure in “Oban” provide an interesting contrast with those on the other two gorillas. Seminiferous tubules were clearly visible and interstitial tissue was less conspicuous in this male (Plate III(a)). Spermatogonia and spermatocytes were identified and in some tubules, small, densely staining spermatid nuclei were present. Although a few spermatid nuclei had neared complete maturation, they were abnormal in shape and the seminiferous epithelium in general showed signs of sloughing and degeneration. Sections of the epididymis exhibited a normally differentiated condition although spermatozoa were absent from the epididymal lumen.

Orang-utan and Chimpanzee The testes from the Orang-utan “Boy” measured 40 x 30 mm (20.8 g) and 41 x 29 mm (20.0 g) while those from the second Orang measured 40 x 29 mm and 41 x 27.5 mm (their weights were not recorded but were probably very similar to the values for “Boy”). Histologically, the testes from both Orang-utans were apparently normal (Plate III(b)). The seminiferous epithelium was active and all the stages of spermatogenesis could be identified. The Chimpanzee testis was similar to those of the Orangs except that the seminiferous tubules of the Chimpanzee appeared to have a greater cross sectional area. In both species the interstitial tissue was inconspicuous. Discussion Only four specimens of captive gorillas have previously been examined to evaluate the structure of the testes and in all cases a degenerate condition was observed (Koch, 1937; McKenney, Traum & Bonestell, 1944; Steiner et al., 1955; Antonius et al., 1971). In the present study, two males exhibited marked atrophy of the seminiferous tubules. An extensive stroma of interhtial cells was present in the testes of both males, but it may not be correct to regard this as hyperplasia, since it is normal for the testes of wild-shot gorillas to contain large amounts of interstitial tissue (Wislocki, 1942; Hall-Craggs, 1962). In the third animal (“Oban”) the testes were structurally more normal and it is

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PLATE111. (a) A light micrograph of the gorilla testis (“Oban”). Some sloughing and degeneration of the seminiferous epithelium is apparent ( x 160). (b) A light micrograph of the Orang-utan testis (“Boy”). The testis is apparently normal in structure ( x 160)

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possible that some apparently degenerate features might have resulted from poor preservation of the material. Nevertheless, the near total absence of late spermatids and the empty epididymal lumen suggests that spermatogenesis was defective in this animal also. Testicular dysfunction may be more common among captive gorillas than is generally realized, but so far only relatively unhealthy specimens have been examined, none of which had sired offspring. Some of the animals were quite young (e.g. “Jojo” approx. 18 years) so that the condition cannot be attributed to senility. Gorillas may live to 30 years of age in the wild and rather longer than this in captivity (Napier & Napier, 1967). Testicular atrophy has not been observed among captive Orang-utans or Chimpanzees, but very few specimens have been examined. It is interesting that only three of the 13 adult male gorillas in British collections are of proven breeding ability (Kingsley, pers. comrn.). Whilst behavioural factors or infertility in the female may also affect breeding success, it is likely that some non-breeding male gorillas are suffering from testicular atrophy. Studies of semen quality would be worthwhile, and it is noteworthy that Seuanez et al. (1977) have shown that semen obtained by electroejaculation from two gorillas contained a high proportion of abnormal spermatozoa, as is also the case in man. It would also be valuable to study the reproductive endocrinology of male gorillas for, apart from McCormack’s (1971) report on testosterone levels in male Chimpanzees, there is very little information on this subject for any of the great apes. In “Guy”, the marked degeneration of the secondary sexual organs, regression of the epididymis and absence of morphologically normal Leydig cells were all consistent with reduced androgen production. However, both “Guy” and “Oban” showed signs that the epididymis had differentiated normally, a process which occurs during puberty under the influence of androgens. Measurements of gonadal and pituitary hormones in living male gorillas might prove instructive. Although it is difficult to obtain blood samples from these animals, it is feasible to measure hormones excreted in the urine. Levels of urinary androgens in “Guy” were very low (Kingsley, pers. comm.). The causes of testicular atrophy in captive gorillas are not known and it is possible that a combination of factors is involved, such as dietary deficiencies, psychological factors, disease or by increased temperatures such as occur in cryptorchidism (Mann, 1964; Waite & Setchell, 1969). Steiner et a/. (1955) suggested that the testicular atrophy they observed in “Bushman”, a 22-year-old gorilla which died at Chicago Zoo, could have resulted from nutritional factors. However, in the present study the male with the most normal testes (“Oban”) was extremely malnourished. He had suffered for some years with gastro-intestinal disease so that he weighed a mere 49 kg at death (Nadler, pers. comm.). Summary

Testes were obtained at post mortem from three Western lowland gorillas, two Bornean Orang-utans and one Chimpanzee. All specimens were adults which had died in captivity. The three gorillas exhibited varying degrees of testicular atrophy whereas the testes of the other great apes were apparently normal in structure. In two gorillas, the semiminiferous tubules were completely atrophic and fibrosed and there was an extensive stroma of interstitial tissue. Observations on one male indicated that the interstitial Leydig cells were non-functional. The accessory sexual organs of this animal were atrophic, indicating an androgen deficiency. Histological studies of the epididymis indicated that differentiation of

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the cells had occurred at puberty, however. In the third gorilla, the testes were structurally more normal but the near absence of spermatids and empty epididymal lumen suggests that spermatogenesis was defective in this animal as well. Testicular dysfunction in captive gorillas may be more common than is generally realized and may contribute to the poor breeding performance of this species in zoos. We are grateful to Mr W. Timmis of Chester Zoo, and Ms C. Ellis, Department of Veterinary Pathology, Liverpool University, for permission to examine material from “Jojo”. Our thanks to Dr R . D. Nadler and Dr H. M. McClure of Yerkes Regional Primate Research Center, for providing material from “Oban”, and to Mrs P. Napier of the British Museum of Natural History who allowed us to examine material from “Oscar”. D. M. Jones and members of the Department of Veterinary Science at the Zoological Society of London kindly allowed us to collect tissues from the other great apes in this study. REFERENCES Antonius, J. I., Ferrier, S. A. & Dillingham, L. A. (1971). Pulmonary embolus and testicular atrophy in a gorilla. Folia primatol. 15: 277-292. Clarke, R. C. (1948). “Alfred” the zoo gorilla. Bristol Med. Chir. J . 65: 19-20. Dym, M. & Romrell, L. 3. (1975). Intra-epithelial lymphocytes in the male reproductive tract of rats and rhesus monkeys. J. Reprod. Fert. 42: 1-7. Hall-Craggs, E. C. B. (1962). The testis of Gorilla gorilla beringei. Proc. zool. Sor. Lond. 139: 51 1-514. Inoue, M. & Hayama, S. (1961-62). Histopathological studies of two mountain gorilla specimens (Gorilla gorilla beringei) “Munidi” and “Emmy”. Primates 3: 29-46. Ito, S . & Karnovsky, M. J. (1968). Formaldehyde fixatives containing trinitro compounds. J. Cell. Biol. 39: 168A. Jones, D. M., Dixson, A. F. & Wadsworth, P. F. (in press). Interstitial cell tumour of the testis in a western lowland gorilla (Gorilla g . gorilla). J. Med. Primatol. Koch, W. (1937). Bericht uber das Ergebnis der Obduktion des gorilla “Bobby” des Zoologischen Gartens zu Berlin. Ein Beitrag zur vergleichenden konstritutionspathologie. Verof. Konst.- Wehrpath. 9: 1-36. Mann, T. (1964). The biochemisfry of semen and the male reproductive tract. London: Methuen. McCormack, S. A. (1971). Plasma testosterone concentration and binding in the chimpanzee; effect of age. Endocrinology 89: 1171-1177. McKenney, F. D., Traum, J. & Bonestell, A. E. (1944). Acute coccidiomycosis in a gorilla (Gorilla beringei) with anatomical notes. J. Am. Vet. Med. Ass. 104: 136-140. Napier, J. R. & Napier, P. H. (1967). A handbook of livingprimates. London: Academic Press. Olney, P. J. S. (Ed.) (1978). Census of rare animals in captivity. Znt. Zoo Yb. 18: 426. Seuanez, H. N., Carothers, A. D., Martin, D. E. & Short, R. V. (1977). Morphological abnormalities in spermatozoa of man and great apes. Nature, Lond. 270: 345-347. Steiner, P. E., Rasmussen, T. B. & Fisher, L. E. (1955). Neuropathy, cardiopathy, hemosiderosis and testicular atrophy in Gorilla gorilla. Arch. Path. 59: 5-25. Waites, G . M. H. & Setchell, B. P. (1969). Some physiological aspects of the function of the testis. In The gonads: 649-714. Mckerns, K. W. (Ed.). New York: Appleton-Century-Crofts. Wislocki, G . B. (1942). Size, weight and histology of the testes in the gorilla. J. Mammal. 23: 281-287.