Sperm-limited males save ejaculates for future matings when competing with superior rivals
Sperm-limited males save ejaculates for future matings when competing with superior rivals
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精子数量有限的雄性在与更优秀的竞争对手竞争时会保存射精以供将来的交配使用
DOI：
10.1016/j.anbehav.2016.12.016
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发表时间：
2017
期刊：
影响因子：
2.5
通讯作者：
M. Taborsky
中科院分区：
文献类型：
--
作者：
D. Schütz;Linda Tschirren;Gudrun Pachler;P. Grubbauer;M. Taborsky
亮点资产阶级雄性鸟巢面临着在当前或未来的交配投资之间的权衡。由于产卵时间过长和高度的一夫多妻制，雄性鸟巢的精子有限。在优势竞争对手的存在下，它们将射精支出减少约50%。鸟巢雄性将精子保存起来，以备未来的交配机会，而不存在寄生性竞争。调整射精以适应精子竞争可能会导致精子受限。特别是在一夫多妻制物种中，雄性可能面临着将精子投资于目前或未来的交配机会之间的权衡。最佳的精子分配决定应该取决于在交配序列中经历的精子竞争的相对强度。在这里，我们询问雄性如何应对一夫多妻制鱼类的这种权衡，选择雄性交配策略，激烈的精子竞争和精子限制。大资产阶级雄性孵化的慈鱼Lamprologus callipterus建造由空蜗牛壳组成的巢，雌性蜗牛在里面产卵和抚养后代。在产卵过程中，雄性鸟巢会将精液释放到贝壳开口中。在基因上不同的是，寄生的矮小雄性在产卵期间进入贝壳，从贝壳内使卵受精。这些矮小的雄性此前被证明是筑巢雄性的更好的精子竞争者。在这里，我们表明，当与多只雌性同时产卵时，雄性巢缩短了每窝的产卵持续时间，每只雌性的射精次数趋于减少，这反映了精子的限制。试验性地将巢雄鸟暴露在与矮小雄鸟的精子竞争中，将射精的次数和持续时间减少了大约一半。因此，当与优势竞争对手竞争时，巢雄鸟并没有像精子竞争风险模型预测的那样增加精子支出，而是像精子竞争强度理论预测的那样，将精子保存到未来的交配机会。这似乎是适应的，因为这一物种对精子的需求相当大，部分原因是他们高度的一夫多妻制。
HighlightsBourgeois nest males face a trade-off between investing in current or future matings.Nest males are sperm limited due to prolonged spawning and a high polygyny level.In the presence of a superior rival, they reduce ejaculate expenditure by ca. 50%.Nest males save sperm for future mating opportunities without parasitic rivals.Adjusting ejaculates to sperm competition can lead to sperm limitation. Particularly in polygynous species, males may face a trade-off between investing sperm in current or future mating opportunities. The optimal sperm allocation decision should depend on the relative intensity of sperm competition experienced in a mating sequence. Here we asked how males respond to this trade-off in polygynous fish with alternative male mating tactics, intense sperm competition and sperm limitation. Large bourgeois males of the shell-brooding cichlid Lamprologus callipterus build nests consisting of empty snail shells, in which females spawn and raise offspring. During spawning, nest males release ejaculates into the shell opening. Genetically distinct, parasitic dwarf males enter shells during spawning to fertilize the eggs from inside the shell. These dwarf males were previously shown to be superior sperm competitors to nest males. Here we showed that when spawning with several females simultaneously, nest males reduced the spawning duration for each clutch and the number of ejaculations per female tended to decrease, reflecting sperm limitation. Experimental exposure of nest males to sperm competition with dwarf males reduced the number and duration of ejaculations by roughly half. Hence, when exposed to competition with a superior rival, nest males did not increase their sperm expenditure as predicted by sperm competition risk models, but in fact saved sperm for future mating opportunities as predicted by sperm competition intensity theory. This seems to be adaptive because of the considerable sperm demands in this species, which is partly due to their high degree of polygyny.