Flexible joints in rigid seaweeds: structure, mechanics, and convergent evolution in articulated coralline algae

人造结构通常是刚性的，经常被海浪的冲击摧毁，但海藻却因其柔韧性而在海浪冲刷的海岸上生存下来。关节珊瑚藻（一种海藻）提供了一个特殊的机会来了解这种灵活性是如何进化的。珊瑚藻有钙化的细胞壁，这使它们默认为刚性的。然而，1亿年前，一些珊瑚进化出了关节，这是一种结构创新，使这些新的灵活藻类能够茁壮成长。事实上，珊瑚海藻的关节进化了三个独立的时期，显然集中在一个共同的机械公式的灵活性，也可能使珊瑚抵抗疲劳损伤，通常伴随着灵活的结构。丹尼的目标是阐明这种衔接的机制，在每三个系的关节珊瑚，使他能够探索和量化的不同方式，这些藻类已经达到了一个共同的机械解决方案。丹尼提议研究组织各级的灵活性机制？从关节中细胞壁的不寻常化学和结构，到关节材料的非凡机械性能，再到整个叶子的结构和动力学。如果这项研究证实，关节珊瑚确实是耐疲劳破坏，它可能会提供指导抗疲劳仿生材料的发展和洞察其他柔性结构的潜在抗疲劳性，生物和人造。在这项研究中使用的生物力学方法是一个理想的背景下，教学生如何科学整合跨领域的知识。丹尼使用这种机械论的观点来教授斯坦福大学本科生的“生态学、进化和植物生物学”课程，并将与圣地亚哥海洋发现研究所合作，利用生物力学作为贫困K-12学生的教学工具。

Manmade structures, which are typically rigid, are often destroyed by the pounding of ocean waves, but seaweeds survive on wave-swept shores by being flexible. Articulated coralline algae (a type of seaweed) provide an exceptional opportunity to understand how this flexibility evolved. Coralline algae have calcified cell walls, which renders them, by default, rigid. However, 100 million years ago, some corallines evolved joints, a structural innovation that allowed these newly flexible algae to thrive. Indeed, joints evolved three separate times in coralline seaweeds, apparently converging on a common mechanical formula for flexibility that may also have allowed corallines to resist the fatigue damage that commonly accompanies flexible structures. Denny aims to elucidate the mechanics of this convergence in each of the three lineages of articulated corallines, allowing him to explore and quantify the different ways in which these algae have arrived at a common mechanical solution. Denny proposes to examine the mechanics of flexibility at all levels of organization?from the unusual chemistry and structure of cell walls in joints, to the extraordinary mechanical properties of joint materials, to the structure and dynamics of whole fronds. If this research confirms that articulated corallines are indeed resistant to fatigue failure, it may provide guidance for the development of fatigue resistant biomimetic materials and insight into the potential fatigue resistance of other flexible structures, both biological and manmade.The biomechanical approach used in this research is an ideal context in which to teach students how science integrates knowledge across fields. Denny uses this mechanistic perspective to teach a course, "Ecology, Evolution, and Plant Biology," for Stanford undergraduates, and will collaborate with the Ocean Discovery Institute of San Diego to exploit biomechanics as a teaching tool for underprivileged K-12 students.