Comparative testis morphometry and seminiferous epithelium cycle length in donkeys and mules.
Abstract: The mule (Equus mulus mulus) is a sterile hybrid domestic animal that results from the breeding of a male donkey (Equus asinus) to a female horse (Equus caballus). Usually, spermatogenesis in mules does not advance beyond spermatocytes. In the present study, we performed a comparative and more accurate morphometric and functional investigation of the testis in donkeys and mules. Due to the smaller testis size, lower seminiferous tubule volume density, and fewer germ cells, the total length of seminiferous tubules in mules was significantly smaller than in donkeys. However, the percentage of seminiferous tubules containing germ cells (spermatogonia and spermatocytes) in mules was approximately 95%. The total number of Sertoli cells per testis observed in donkeys and mules was very similar. However, the total number of Leydig cells in mules was approximately 70% lower than in donkeys. At least in part, this difference was probably related to the lower number of germ cells present in mule seminiferous tubules. Although spermatogenesis in mules did not advance beyond secondary spermatocytes/newly formed round spermatids, germ cell associations in the seminiferous epithelium and pachytene spermatocytes nuclear volume in donkeys and mules were similar. The duration of spermatogenesis was estimated using intratesticular injections of tritiated thymidine. Each spermatogenic cycle in donkeys lasted 10.5 days. A similar value was found in mules ( approximately 10.1 days). Considering that the entire spermatogenic process takes approximately 4.5 cycles to be completed, its total duration in donkeys was estimated to last 47.2 days. The results found for mules suggest that the mechanisms involved in the determination of testis structure and function are probably originated from donkeys. Also, the data found for mules suggest that their seminiferous tubules are able to sustain complete spermatogenesis. In this regard, this species is a potential model for transplants of germ cells originated from donkeys and horses or other large animals.
Publication Date: 2002-06-25 PubMed ID: 12080024DOI: 10.1095/biolreprod67.1.247Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study compares testis size, structure, and function between donkeys and mules, noting fundamental differences and potential reasons for mules’ sterility. Despite the similar spermatogenesis process duration, mules’ seminiferous tubules accommodate fewer germ cells and Leydig cells.
Overview of the Study
- The research carried out a comparative and more precise investigation of the testis structure and function in donkeys and mules (sterile hybrid animal born out of breeding a male donkey and a female horse).
- The assessment showed significant size differences in the seminiferous tubules, with mules having considerably smaller tubules than donkeys, largely due to their smaller testis size, decreased volume density of seminiferous tubules, and a smaller number of germ cells.
Spermatogenesis in Donkeys and Mules
- In terms of spermatogenesis, the study notes that the process in mules often does not progress beyond spermatocytes. However, an estimated 95% of their seminiferous tubules contained germ cells (spermatogonia and spermatocytes).
- Despite the halted process at secondary spermatocytes/newly formed round spermatids, mules and donkeys had similar germ cell associations in the seminiferous epithelium and pachytene spermatocytes nuclear volume.
- The spermatogenic cycle in both animals lasted about 10 days, taking around 4.5 cycles to fully complete, which equated to about 47.2 days in donkeys.
Sertoli and Leydig Cells
- Another observation made in the study was the similar total number of Sertoli cells present in the testis of both donkeys and mules.
- The number of Leydig cells in mules, however, was about 70% less than in donkeys, which is likely attributed to the decreased number of germ cells present in mules’ seminiferous tubules.
Conclusions and Further Implications
- The differences noticed in the study imply that the mechanisms determining testis structure and function in mules likely originate from donkeys.
- Despite their sterility, the ability of the mules’ seminiferous tubules to sustain complete spermatogenesis suggest them as potential models for transplants of germ cells originated from donkeys, horses, or other large animals.
Cite This Article
APA
Neves ES, Chiarini-Garcia H, França LR.
(2002).
Comparative testis morphometry and seminiferous epithelium cycle length in donkeys and mules.
Biol Reprod, 67(1), 247-255.
https://doi.org/10.1095/biolreprod67.1.247 Publication
Researcher Affiliations
- Laboratory of Cellular Biology, Department of Morphology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil 31270-901.
MeSH Terms
- Animals
- Apoptosis / physiology
- Cell Count
- Cell Nucleus / physiology
- Cell Nucleus / ultrastructure
- Equidae / physiology
- Leydig Cells / physiology
- Male
- Seminiferous Epithelium / anatomy & histology
- Seminiferous Epithelium / drug effects
- Seminiferous Epithelium / physiology
- Seminiferous Tubules / anatomy & histology
- Seminiferous Tubules / drug effects
- Seminiferous Tubules / physiology
- Sertoli Cells / physiology
- Spermatocytes / physiology
- Spermatocytes / ultrastructure
- Spermatogenesis / physiology
- Testis / anatomy & histology
- Testis / drug effects
- Testis / physiology
- Thymidine / pharmacology
- Y Chromosome / physiology
Citations
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