Sex and Evolution Research Group, Natural History Museum, University of Oslo, 0318 Oslo, Norway.
Macaronesian Institute of Field Ornithology, 38001 Santa Cruz de Tenerife, Canary Islands, Spain.
Cells. 2021 May 31;10(6):1358. doi: 10.3390/cells10061358.
Sperm swimming performance affects male fertilization success, particularly in species with high sperm competition. Understanding how sperm morphology impacts swimming performance is therefore important. Sperm swimming speed is hypothesized to increase with total sperm length, relative flagellum length (with the flagellum generating forward thrust), and relative midpiece length (as the midpiece contains the mitochondria). We tested these hypotheses and tested for divergence in sperm traits in five island populations of Canary Islands chiffchaff (). We confirmed incipient mitochondrial DNA differentiation between Gran Canaria and the other islands. Sperm swimming speed correlated negatively with total sperm length, did not correlate with relative flagellum length, and correlated negatively with relative midpiece length (for Gran Canaria only). The proportion of motile cells increased with relative flagellum length on Gran Canaria only. Sperm morphology was similar across islands. We thus add to a growing number of studies on passerine birds that do not support sperm morphology-swimming speed hypotheses. We suggest that the swimming mechanics of passerine sperm are sufficiently different from mammalian sperm that predictions from mammalian hydrodynamic models should no longer be applied for this taxon. While both sperm morphology and sperm swimming speed are likely under selection in passerines, the relationship between them requires further elucidation.
精子游动性能影响雄性受精成功率，尤其是在精子竞争激烈的物种中。因此，了解精子形态如何影响游动性能非常重要。游动速度被认为与总精子长度、相对鞭毛长度（鞭毛产生向前推力）和相对中段长度（因为中段含有线粒体）呈正相关。我们在加那利群岛的五个雀形目 chiffchaff 岛种群中检验了这些假设，并检验了精子特征的分歧。我们证实了Gran Canaria 与其他岛屿之间的线粒体 DNA 分化。精子游动速度与总精子长度呈负相关，与相对鞭毛长度无关，与相对中段长度（仅在 Gran Canaria 呈负相关）。只有在 Gran Canaria，运动细胞的比例与相对鞭毛长度呈正相关。精子形态在各岛屿之间相似。因此，我们为越来越多的雀形目鸟类研究增加了一个不支持精子形态-游动速度假说的证据。我们认为，雀形目精子的游动力学与哺乳动物精子有很大的不同，因此不应再将哺乳动物流体动力学模型的预测应用于该分类群。虽然精子形态和精子游动速度在雀形目鸟类中都可能受到选择，但它们之间的关系需要进一步阐明。
