Sperm competition risk drives rapid ejaculate adjustments mediated by seminal fluid (2017)
Type of ContentJournal Article
- Science: Journal Articles 
© Bartlett et al. In many species, males can make rapid adjustments to ejaculate performance in response to sperm competition risk; however, the mechanisms behind these changes are not understood. Here, we manipulate male social status in an externally fertilising fish, chinook salmon (Oncorhynchus tshawytscha), and find that in less than 48 hr, males can upregulate sperm velocity when faced with an increased risk of sperm competition. Using a series of in vitro sperm manipulation and competition experiments, we show that rapid changes in sperm velocity are mediated by seminal fluid and the effect of seminal fluid on sperm velocity directly impacts paternity share and therefore reproductive success. These combined findings, completely consistent with sperm competition theory, provide unequivocal evidence that sperm competition risk drives plastic adjustment of ejaculate quality, that seminal fluid harbours the mechanism for the rapid adjustment of sperm velocity and that fitness benefits accrue to males from such adjustment.
KeywordsOncorhynchus tshawytscha; ejaculate quality; evolutionary biology; genomics; seminal fluid; social status; sperm competition; sperm velocity
ANZSRC Fields of Research30 - Agricultural, veterinary and food sciences::3005 - Fisheries sciences::300504 - Fish physiology and genetics
07 - Agricultural and Veterinary Sciences::0702 - Animal Production::070201 - Animal Breeding
RightsCopyright Bartlett et al. This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.
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