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

人造建筑通常是刚性的，经常被海浪的冲击摧毁，但海藻却因其柔性而在海浪冲刷的海岸上生存下来。铰接珊瑚藻（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，这使得它们在默认情况下是刚性的。然而，1亿年前，一些珊瑚进化出了关节，这是一种结构上的创新，使这些新的灵活的藻类得以茁壮成长。事实上，珊瑚海藻的关节进化了三次，显然是趋同于一个共同的柔韧性力学公式，这可能也使珊瑚能够抵抗通常伴随柔性结构而来的疲劳损伤。Denny的目标是阐明三种铰接珊瑚谱系中这种融合的机制，使他能够探索和量化这些藻类达到共同机械解决方案的不同方式。丹尼建议在组织的各个层面检查灵活性的机制。从接头中细胞壁的不同寻常的化学和结构，到接头材料的不同寻常的机械性能，再到整片叶子的结构和动力学。如果这项研究证实了关节珊瑚确实具有抗疲劳破坏的能力，那么它可能为抗疲劳仿生材料的开发提供指导，并为其他生物和人造柔性结构的潜在抗疲劳能力提供见解。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。丹尼用这种机械的观点为斯坦福大学的本科生教授一门课程，“生态学、进化和植物生物学”，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的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.