Sperm macrocephaly syndrome in the ostrich Struthio camelus: morphological characteristics and implications for motility

L. du Plessis, M. Bonato, C. Durandt, S. W. P. Cloete and J. T. Soley

Electron Microscope Unit, Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa; Department of Animal Sciences, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; Department of Immunology, Institute for Cellular and Molecular Medicine, Faculty of Health Sciences, SAMRC Extramural Unit for Stem Cell Research and Therapy, University of Pretoria, South Africa; Directorate Animal Sciences: Elsenburg, Private Bag X1, Elsenburg 7607, South Africa; Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa

Abstract: Sperm macrocephaly syndrome (SMS) is characterised by a high percentage of spermatozoa with enlarged heads and multiple tails, and is related to infertility. Although this multiple sperm defect has been described in other mammalian species, little is known about this anomaly in birds. Morphological examination of semen from nine South African black ostriches (Struthio camelus var. domesticus) involved in an AI trial revealed the variable presence of spermatozoa with large heads and multiple tails. Ultrastructural features of the defect were similar to those reported in mammals except that the multiple tails were collectively bound within the plasmalemma. The tails were of similar length and structure to those of normal spermatozoa, and the heads were 1.6-fold longer, emphasising the uniformity of the anomaly across vertebrate species. Flow cytometry identified these cells as diploid and computer-aided sperm analysis revealed that they swim slower but straighter than normal spermatozoa, probably due to the increased drag of the large head and constrained movement of the merged multiple tails. The high incidence of this defect in one male ostrich indicates that, although rare, SMS can occur in birds and may potentially have an adverse effect on breeding programs, particularly for endangered species.

Reproduction, Fertility and Development 31(4) 712-723 https://doi.org/10.1071/RD18242
Submitted: 26 June 2018 / Accepted: 23 October 2018 / Published: 21 November 2018