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The ovulated ovum of the horse: cytology of nonfertilized ova to pronuclear stage ova.
Abstract: Fertilization and early development in the horse were studied by recovering oviductal ova at various times after postovulatory mating. Ova collected between 7 and 22 h post coitum (pc) were examined for evidence of fertilizing sperm, cellular changes accompanying fertilization, and pronuclear development. Five ova collected between 7 and 9 h pc contained a marginal metaphase plate, but had no indication of sperm components; three of these, however, showed reduced numbers of cortical granules. Two activated ova (10 and 14 h pc) were in telophase of the second meiotic division, following incorporation of the fertilizing sperm. The fertilizing sperm was situated in a slight elevation; the nucleus was expanding but lacked a nuclear envelope. The pronuclear stage in the horse began as early as 12 h pc, and lasted at least until 21 h pc. Sperm tail remnants were seen in 5 of 7 pronuclear-stage ova, although the crowding of the cytoplasm with clusters of lipid and vacuoles made discerning sperm tail remnants difficult. The spindles of the metaphase stage of the second meiotic division were oriented radially, that is, at right angles to the cell surface, in all but one ovum, so this orientation is not a response to fertilization.
Publication Date: 1987-09-01 PubMed ID: 3676399DOI: 10.1095/biolreprod37.2.453Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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The research article explores the process of fertilization and early development in the horse by examining ova collected at different times after mating. A closer look at the eggs reveals sperm presence, cellular changes tied to fertilization, and the development of pronuclei.
Methodology
- The study revolves around the collection and examination of oviductal ova (eggs) from horses, obtained at varying periods after postovulatory mating.
- These eggs, collected between 7 and 22 hours post coitum (pc), were studied for signs of fertilizing sperm, cellular transformations related to fertilization, and pronuclear evolution.
Observations and Findings
- Five ova gathered between 7 and 9 hours pc showed a marginal metaphase plate, with no traces of sperm elements; however, three of these exhibited a decrease in the number of cortical granules.
- Two activated ova (10 and 14 hours pc) entered the telophase stage of the second meiotic division, subsequent to the incorporation of the fertilizing sperm.
- An observed characteristic was a slight elevation where the fertilizing sperm was located; the sperm nucleus was expanding but missing a nuclear envelope.
- The pronuclear stage in horses was noted to start as early as 12 hours pc and lasted at least until 21 hours pc.
- The presence of remnants of sperm tails was recorded in 5 out of 7 pronuclear-stage eggs, but identifying these remnants was found to be challenging due to crowding of the cytoplasm by clusters of lipid and vacuoles.
- The spindles of the metaphase stage during the second meiotic division were radially oriented, meaning, at right angles to the cell surface, in every ovum except one, implying that this orientation is independent of fertilization.
Conclusion
- The study provides a detailed account of fertilization in horses, shedding light on various aspects like the position of the fertilizing sperm, changes in cellular structures upon fertilization, and the pronuclear stage of development.
- The research adds to the understanding of reproduction in horses, and could potentially aid in further studies or development of enhanced breeding techniques.
Cite This Article
APA
Enders AC, Liu IK, Bowers J, Lantz KC, Schlafke S, Suarez S.
(1987).
The ovulated ovum of the horse: cytology of nonfertilized ova to pronuclear stage ova.
Biol Reprod, 37(2), 453-466.
https://doi.org/10.1095/biolreprod37.2.453 Publication
Researcher Affiliations
- Department of Human Anatomy, School of Medicine, University of California, Davis 95616.
MeSH Terms
- Animals
- Copulation
- Fertilization
- Horses / physiology
- Microscopy, Electron
- Microscopy, Electron, Scanning
- Ovum / cytology
- Reference Values
Grant Funding
- HD 10342 / NICHD NIH HHS
Citations
This article has been cited 5 times.- Felix MR, Turner RM, Dobbie T, Hinrichs K. Successful in vitro fertilization in the horse: production of blastocysts and birth of foals after prolonged sperm incubation for capacitation†. Biol Reprod 2022 Dec 10;107(6):1551-1564.
- Benammar A, Derisoud E, Vialard F, Palmer E, Ayoubi JM, Poulain M, Chavatte-Palmer P. The Mare: A Pertinent Model for Human Assisted Reproductive Technologies?. Animals (Basel) 2021 Aug 4;11(8).
- Salgado RM, Brom-de-Luna JG, Resende HL, Canesin HS, Hinrichs K. Lower blastocyst quality after conventional vs. Piezo ICSI in the horse reflects delayed sperm component remodeling and oocyte activation. J Assist Reprod Genet 2018 May;35(5):825-840.
- Ruggeri E, DeLuca KF, Galli C, Lazzari G, DeLuca JG, Stokes JE, Carnevale EM. Use of Confocal Microscopy to Evaluate Equine Zygote Development After Sperm Injection of Oocytes Matured In Vivo or In Vitro. Microsc Microanal 2017 Dec;23(6):1197-1206.
- Delimitreva S, Chakarova I. How Cytoskeletal Disorders Contribute to Errors in the Chromosomal Segregation of Oocytes and Cleavage Stage Embryos. J Dev Biol 2025 Dec 2;13(4).
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