Assessing the potential for egg chemoattractants to mediate sexual selection in a broadcast spawning marine invertebrate
Assessing the potential for egg chemoattractants to mediate sexual selection in a broadcast spawning marine invertebrate
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DOI：
10.1098/rspb.2012.0181
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发表时间：
2012-07-22
影响因子：
4.7
通讯作者：
Fitzpatrick, John L.
中科院分区：
文献类型：
--
作者：
Evans, Jonathan P.;Garcia-Gonzalez, Francisco;Fitzpatrick, John L.
在许多物种中，卵子趋化剂在引导精子走向未受精卵（精子趋化性）方面起着关键作用。到目前为止，已知的精子趋化功能包括增加卵子的有效目标大小，从而促进精子与卵子的相遇，并促进物种识别。在这里，我们报道了在广播产卵的贻贝，Mytilus galloprovincialis中，卵子化学引诱剂可能在性选择中发挥了不可预见的作用，使精子能够有效地“选择”不同同种雌性的卵子。在最初的实验中，我们证实了精子趋化性发生在M. galloprovincialis中，通过显示精子被吸引到未受精卵，当在二分室中选择卵子或没有卵子时。然后，我们进行了两个交叉分类的交配实验，每个实验都包括相同的雄性和雌性在相同的雄性和雌性组合中杂交，但在实验条件下，精子“没有选择”（每次受精试验都在培养皿中进行，涉及单个雄性和雌性）或“选择”雌性的卵子（精子被放置在二分选择室的中心，允许从不同的雌性中选择卵子）。我们发现，在两个实验中，雄性与雌性的相互作用决定了受精率，并且在选择卵子实验中的精子迁移模式与不选择卵子实验中的受精率之间存在显著的一致性。因此，在精子与卵子的直接接触中，精子似乎利用化学线索优先游向与它们最相容的卵子。这些结果表明，精子在化学因素的基础上选择卵子的差异，从而揭示了卵子化学引诱剂介导基因相容伴侣的配偶选择的潜力。鉴于精子趋化性在不同分类群中的普遍存在，我们的发现可能对其他交配系统中的性选择具有广泛的意义。
In numerous species, egg chemoattractants play a critical role in guiding sperm towards unfertilized eggs (sperm chemotaxis). Until now, the known functions of sperm chemotaxis include increasing the effective target size of eggs, thereby promoting sperm-egg encounters, and facilitating species recognition. Here, we report that in the broadcast spawning mussel, Mytilus galloprovincialis, egg chemoattractants may play an unforeseen role in sexual selection by enabling sperm to effectively 'choose' between the eggs of different conspecific females. In an initial experiment, we confirmed that sperm chemotaxis occurs in M. galloprovincialis by showing that sperm are attracted towards unfertilized eggs when given the choice of eggs or no eggs in a dichotomous chamber. We then conducted two cross-classified mating experiments, each comprising the same individual males and females crossed in identical male x female combinations, but under experimental conditions that offered sperm 'no-choice' (each fertilization trial took place in a Petri dish and involved a single male and female) or a 'choice' of a female's eggs (sperm were placed in the centre of a dichotomous choice chamber and allowed to choose eggs from different females). We show that male-by-female interactions characterized fertilization rates in both experiments, and that there was remarkable consistency between patterns of sperm migration in the egg-choice experiment and fertilization rates in the no-choice experiment. Thus, sperm appear to exploit chemical cues to preferentially swim towards eggs with which they are most compatible during direct sperm-to-egg encounters. These results reveal that sperm differentially select eggs on the basis of chemical cues, thus exposing the potential for egg chemoattractants to mediate mate choice for genetically compatible partners. Given the prevalence of sperm chemotaxis across diverse taxa, our findings may have broad implications for sexual selection in other mating systems.