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Asian Journal of Andrology (2013) 15, 152β154; doi:10.1038/aja.2012.109; published online 3 December 2012
Sperm speed is associated with sex bias of siblings in a human population
Jim A Mossman1,2, Jon Slate2, Tim R Birkhead2, Harry D Moore3 and Allan A Pacey4
1 Department of Ecology and Evolutionary Biology, Box G, Brown University, Providence, Rhode Island 02912, USA
2 Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
3 Centre for Stem Cell Biology, Department of Biomedical Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
4 Academic Unit of Reproductive and Developmental Medicine, Department of Human Metabolism, School of Medicine and Biomedical Sciences, Sheffield S10 2SF, UK
Correspondence: Dr JA Mossman, (Jim_Mossman@brown.edu)
Received 18 May 2012; Revised 30 July 2012; Accepted 24 August 2012
Advance online publication 3 December 2012
| Abstract |
Recent studies investigating possible causes of male subfertility have largely focused on how lifestyle or environmental factors impact on the process of spermatogenesis. Markedly, fewer studies have investigated those risk factors that result in reduced sperm quality, such as poor sperm motility. The speed at which sperm swim is a major predictor of fertility and is extremely variable in human populations. It has been hypothesized that offspring sex may be adaptively manipulated to maximize the offspring's reproductive fitness (e.g., parents with genes for good male fertility traits, such as high sperm speed, would produce primarily sons and fewer daughters because the offspring will inherit advantageous male fertility genes). Conversely, parents with poor male fertility genes would produce primarily daughters. We tested whether there was an association between how fast a man's sperm swam and the sex bias of his siblings in a sample of men attending clinic for fertility investigations with their partner and with a wide range of semen characteristics, including sperm speed. We found that the sex bias of a man's siblings is associated with his sperm speed; men with female-biased siblings had significantly slower sperm (judged using computer-assisted sperm analysis (CASA)) than men from male-biased sibships. This observation suggests family composition is an important factor that needs to be considered in future epidemiological and clinical studies of human fertility.
Keywords: computer-assisted sperm analysis (CASA); fertility; intralocus sexual conflict; male; offspring; sex ratio; sexual antagonism |
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