Semen Assessments
Morphology is assessed using phase contrast microscopy. Spermatozoa are fixed in paraformaldehyde, and 100 cells are visualised and assessed for any morphological abnormalities. Sperm head abnormalities (A) are indicative of damage to sperm nucleus and/or acrosome. Mid-piece abnormalities (B), such as damaged, bent or coiled mid-pieces, are reveal damage to the energy producing mitochondria, while tail abnormalities (C) indicate impaired forward motility. The presence of cytoplasmic droplets (D, E) are indicative of incomplete sperm maturation. Morphological abnormalities are associated with increased DNA damage [2], higher reactive oxygen species (ROS) production [3], and lower pregnancy rates [1]. Tang [4] reported chromosomal abnormalities and DNA fragmentation to be significantly higher in morphologically abnormal spermatozoa. Below are examples of some common morphological defects which result in impaired fertilising potential. (Images adapted from Brito 2007 [5])
1. Love, C.C. (2011) Relationship between sperm motility, morphology and the fertility of stallions. Theriogenology. 76(3): p. 547-557.
2. Enciso, M., Cisale, H., Johnston, S.D., Sarasa, J., Fernández, J.L., and Gosálvez, J. (2011) Major morphological sperm abnormalities in the bull are related to sperm DNA damage. Theriogenology. 76(1): p. 23-32.
3. Aziz, N., Saleh, R.A., Sharma, R.K., Lewis-Jones, I., Esfandiari, N., Thomas, A.J., and Agarwal, A. (2004) Novel association between sperm reactive oxygen species production, sperm morphological defects, and the sperm deformity index. Fertility and Sterility. 81(2): p. 349-354.
4. Tang, S.S., Gao, H., Zhao, Y., and Ma, S. (2010) Aneuploidy and DNA fragmentation in morphologically abnormal sperm. International Journal of Andrology. 33(1): p. e163-e179.
5. Brito, L.F.C. (2007) Evaluation of Stallion Sperm Morphology. Clinical Techniques in Equine Practice. 6(4): p. 249-264.