Novel Defense Mechanisms in the Armor of the Scales of the “Living Fossil” Coelacanth Fish,Advanced Functional Materials

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Novel Defense Mechanisms in the Armor of the Scales of the “Living Fossil” Coelacanth Fish
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2018-09-25 , DOI: 10.1002/adfm.201804237
Haocheng Quan ₁ , Wen Yang _{2,

3} , Eric Schaible ₄ , Robert O. Ritchie _{3,

5} , Marc A. Meyers _{1,

2,

6}

Affiliation

Here, experiments and analysis revealing the unique defense mechanisms of the coelacanth, a lobe‐finned fish termed a “living fossil”, are reported, as it was considered to be extinct until 1938, but extant for 400 million years. This defense is provided by primitive elasmoid scales having a rare double‐twisted Bouligand structure of lamellae which provides extraordinary resistance to deformation without failure. Distinct from other elasmoid scales, the collagen fibrils in the coelacanth fish scales form bundles which are embedded in a matrix comprising fibers arranged perpendicular to the layered (double‐twisted Bouligand) structure that provide added rigidity and resistance to deformation. Using in situ synchrotron small‐angle X‐ray scattering during uniaxial tensile testing, the deformation mechanisms of the collagen are identified in terms of fibril stretching, reorientation, sliding, bending, and delamination. The unique structure of the coelacanth scales, distinct from modern elasmoid scales such as the carp, provides a variety of mechanisms to arrest cracking, making it an outstanding damage‐tolerant material to resist predator attacks.

中文翻译：

“活化石”腔棘鱼鳞甲的新型防御机制

在这里，进行了实验和分析，揭示了腔棘鱼的独特防御机制，腔棘鱼被称为“活化石”，它被认为已灭绝，直到1938年，但已经存在了4亿年。这种防御作用是由具有罕见的双螺旋片状Bouligand结构的原始弹力体鳞片提供的，该结构对变形没有破坏提供了出色的抵抗力。与其他弹性体鳞片不同，腔棘鱼鳞片中的胶原原纤维形成束，这些束被包埋在基质中，基质中的纤维垂直于分层结构（双捻布立根）排列，从而增加了刚度和抗变形能力。在单轴拉伸试验中使用原位同步加速器小角度X射线散射，胶原蛋白的变形机制是根据原纤维的拉伸，重新定向，滑动，弯曲和分层来确定的。腔棘鱼鳞片的独特结构不同于鲤鱼等现代弹性鳞片鳞屑，它提供了多种阻止裂纹的机制，使其成为抵抗食肉动物攻击的出色的耐伤害材料。

更新日期：2018-09-25

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