Abstract
Game theory models of sperm competition predict that within species, males should increase their sperm expenditure when they have one competitor, but decrease expenditure with increasing numbers of competitors. So far, there have been few tests or support for this prediction. Here, we show that males of a freshwater fish, the European bitterling, Rhodeus sericeus, do indeed adjust their ejaculation rate to the number of male competitors by first increasing and then decreasing their ejaculation rates as the number of competitors increases. However, this occurred only under restricted conditions. Specifically, the prediction was upheld as long as no female had deposited eggs in the live mussels that are used as spawning sites. After one or more females had spawned, males did not decrease their ejaculation rates with the number of competitors, but instead they became more aggressive. This indicates that decreased ejaculation rate and increased aggression are alternative responses to increased risk of sperm competition.
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Selected References
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- Ball M. A., Parker G. A. Sperm competition games: inter- and intra-species results of a continuous external fertilization model. J Theor Biol. 1997 Jun 21;186(4):459–466. doi: 10.1006/jtbi.1997.0406. [DOI] [PubMed] [Google Scholar]
- doi: 10.1098/rspb.1997.0166. [DOI] [PMC free article] [Google Scholar]
- doi: 10.1098/rspb.1998.0585. [DOI] [PMC free article] [Google Scholar]
- doi: 10.1098/rspb.1999.0740. [DOI] [PMC free article] [Google Scholar]
- Parker G. A., Ball M. A., Stockley P., Gage M. J. Sperm competition games: a prospective analysis of risk assessment. Proc Biol Sci. 1997 Dec 22;264(1389):1793–1802. doi: 10.1098/rspb.1997.0249. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Warner R. R., Shapiro D. Y., Marcanato A., Petersen C. W. Sexual conflict: males with highest mating success convey the lowest fertilization benefits to females. Proc Biol Sci. 1995 Nov 22;262(1364):135–139. doi: 10.1098/rspb.1995.0187. [DOI] [PubMed] [Google Scholar]