Morphological asymmetry in raphid pennate diatoms is detectable not only by valve outline and specific frustule features, but also in their ontogeny. All raphid pennate diatoms exhibit cryptic lateral polarity, which is associated with the asymmetric formation of the valve sides along the apical axis. Differences in the relative widths of primary and secondary valve sides have proven taxonomically important for separating dorsiventral genera within the Cymbellales. However, rigorous studies examining subtle asymmetric differences in valve outline are scarce. In the present geometric morphometric study of 23 Luticola species, the total asymmetry in valve outline of natural populations was decomposed into components of directional asymmetry (DA) and fluctuating asymmetry (FA) to test whether cryptic directional asymmetry has a significant effect on valve outlines across the genus as a whole. The patterns of asymmetric variation provide a view on average asymmetry of populations (evaluated by DA) and individual asymmetric deviations (associated with FA). Subtle, but statistically significant, average irregularities between the primary and secondary sides of Luticola species (i.e., the effect of DA) were found in all but two species. Patterns of DA between valve sides were quite similar in 17 of the analysed species. This likely indicates common developmental patterns in their morphogenesis. The effect of FA, which has often been used as a proxy of developmental instability of populations, was significant in all Luticola species. Since FA scores of individual cells were not correlated with size diminution of most species, FA might reflect the effect of environmental factors but not life cycle changes. The methodological framework presented in this study could be valuable for future work focused on evolutionarily and/or environmentally related shape aberrations and valve variation in pennate diatoms.

中文翻译：

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Luticola 物种的不对称性

针状羽状硅藻的形态不对称不仅可以通过瓣膜轮廓和特定的硅藻壳特征来检测，还可以通过它们的个体发育来检测。所有 raphid 羽状硅藻都表现出隐秘的横向极性，这与沿顶轴的瓣膜侧的不对称形成有关。初级和次级瓣膜侧相对宽度的差异已证明对于分离 Cymbellales 内的背腹属具有重要的分类学意义。然而，很少有严格的研究检查瓣膜轮廓的细微不对称差异。在目前对 23 种 Luticola 物种的几何形态测量研究中，自然种群瓣膜轮廓的总不对称性被分解为方向不对称（DA）和波动不对称（FA）的组成部分，以测试神秘的方向不对称性是否对整个属的瓣膜轮廓有显着影响。不对称变异的模式提供了总体（由 DA 评估）和个体不对称偏差（与 FA 相关）的平均不对称性的视图。在除两个物种外的所有物种中都发现了 Luticola 物种的初级和次级侧之间的微妙但具有统计学意义的平均不规则性（即 DA 的影响）。在分析的 17 个物种中，瓣膜两侧的 DA 模式非常相似。这可能表明它们的形态发生中存在共同的发育模式。FA的作用，它经常被用作种群发育不稳定性的代表，在所有 Luticola 物种中都很重要。由于单个细胞的 FA 分数与大多数物种的大小减小无关，因此 FA 可能反映环境因素的影响，而不是生命周期的变化。本研究中提出的方法学框架对于未来关注羽状硅藻的进化和/或环境相关形状畸变和瓣膜变异的工作可能是有价值的。