Abrams Michael J, Basinger Ty, Yuan William, Guo Chin-Lin, Goentoro Lea
Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125;
Trinity College, University of Oxford, Oxford OX1 3BH, United Kingdom;
Proc Natl Acad Sci U S A. 2015 Jun 30;112(26):E3365-73. doi: 10.1073/pnas.1502497112. Epub 2015 Jun 15.
What happens when an animal is injured and loses important structures? Some animals simply heal the wound, whereas others are able to regenerate lost parts. In this study, we report a previously unidentified strategy of self-repair, where moon jellyfish respond to injuries by reorganizing existing parts, and rebuilding essential body symmetry, without regenerating what is lost. Specifically, in response to arm amputation, the young jellyfish of Aurelia aurita rearrange their remaining arms, recenter their manubria, and rebuild their muscular networks, all completed within 12 hours to 4 days. We call this process symmetrization. We find that symmetrization is not driven by external cues, cell proliferation, cell death, and proceeded even when foreign arms were grafted on. Instead, we find that forces generated by the muscular network are essential. Inhibiting pulsation using muscle relaxants completely, and reversibly, blocked symmetrization. Furthermore, we observed that decreasing pulse frequency using muscle relaxants slowed symmetrization, whereas increasing pulse frequency by lowering the magnesium concentration in seawater accelerated symmetrization. A mathematical model that describes the compressive forces from the muscle contraction, within the context of the elastic response from the mesoglea and the ephyra geometry, can recapitulate the recovery of global symmetry. Thus, self-repair in Aurelia proceeds through the reorganization of existing parts, and is driven by forces generated by its own propulsion machinery. We find evidence for symmetrization across species of jellyfish (Chrysaora pacifica, Mastigias sp., and Cotylorhiza tuberculata).
当动物受伤并失去重要结构时会发生什么？一些动物只是简单地愈合伤口，而另一些动物则能够再生失去的部分。在这项研究中，我们报告了一种以前未被识别的自我修复策略，即月亮水母通过重新组织现有部分来应对损伤，并重建基本的身体对称性，而不是再生失去的部分。具体来说，作为对触须切断的反应，海月水母的幼体重新排列它们剩余的触须，将它们的口腕重新居中，并重建它们的肌肉网络，所有这些都在12小时到4天内完成。我们将这个过程称为对称化。我们发现对称化不是由外部线索、细胞增殖、细胞死亡驱动的，即使移植了异体触须也会进行。相反，我们发现肌肉网络产生的力是必不可少的。使用肌肉松弛剂完全且可逆地抑制搏动会阻止对称化。此外，我们观察到使用肌肉松弛剂降低搏动频率会减缓对称化，而通过降低海水中的镁浓度增加搏动频率会加速对称化。一个数学模型，在中胶层的弹性响应和碟状幼体几何形状的背景下，描述了肌肉收缩产生的压缩力，可以概括整体对称性的恢复。因此，海月水母的自我修复是通过现有部分的重新组织进行的，并由其自身推进机制产生的力驱动。我们发现了水母物种（太平洋黄金水母、乳头真囊水母和瘤手水母）中对称化的证据。
