Adjustments of ejaculation rates in response to risk of sperm competition in a fish, the bitterling (Rhodeus sericeus)

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Proceedings of the Royal Society of London Series B 269 (1500): 1549-1553

Title: Adjustments of ejaculation rates in response to risk of sperm competition in a fish, the bitterling (Rhodeus sericeus)
Author: Candolin, Ulrika; Reynolds, John D.
ISSN: 0962-8452
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 sh, the European bitterling, Rhodeus sericeus, do indeed adjust their ejaculation rate to the number of male competitors by rst increasing and then decreasing their ejaculation rates as the number of competitors increases. However, this occurred only under restricted conditions. Speci cally, 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.
URI: http://hdl.handle.net/1975/144
Date: 2002-06-28
Subject: alternative reproductive behaviours
mate guarding
sexual selection
trade-offs
Cyprinidae
Unionidae


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