 Reference Base  Testicular morphology of a Greater Indian rhinoceros (Rhi... |
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| Location: |
World |
| Subject: |
Reproduction |
| Species: |
Indian Rhino |
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In old male Rhinoceros unicornis. Spermatogenesis has not been examined in the histological level in any species of rhinoceroses. While spermatogenesis has been examined in the equine species that belong to the same order Perrisodactyla as rhinoceroses, and the quantitative studies of spermatogonia subtypes has attracted many investigators. However, we were not able to distinguish the common histological character of spermatogenesis specific to the perrisodactyls from these data. The equine spermatogenesis was considered to be useful to elucidate its seasonal change mechanism, while the seasonality in reproductive activity of greater Indian rhinoceros has not been reported in any zoo. It was reported that numbers of each subtype of spermatogonia and primary spermatocytes decreases obviously in non-breeding season in horses 1121. However, such seasonal inactivity of seminiferous tubules in horses may not be consistent with the germ cell confusion on rhinoceros spermatogenesis.
We suspect that ageing may associate with the germ cell confusion in spermatogenesis, extraordinary collagen fiber development, and occurrence of many free cells in the interstitial space. Age-related changes in testicular morphology have been investigated in human, mouse and stallion, indicating that ageing lead to the regression of seminiferous tubules due to germ cell degeneration. The present results may not be related to the germ cell necrosis.
Because the lumen of seminiferous tubules was closed, we suggest that the fluid secretion from Sertoli cells is severely interrupted. The fluid secretion is functionally dependent on the Sertoli cell microtubules, this findings may be caused by the damage of Sertoli cell cytoskeleton.
This species numbered only about 1,600 individuals and is classified as endangered. So, the present basic morphological data of abnormal spermatogenesis are expected to be useful for reproduction and a conservation of this species, because the development and birth of normal animals have also been indicated by the oocyte-round spermatid fusion in rodents.
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