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The coconut crab has black protrusions on the tops of its walking legs and claw fingers. In addition, there are regularly aligned small black protrusions on part of the exoskeleton surface of the claws and leg. The elemental composition, crystal structure, tissue structure, and mechanical properties of these protrusions were studied using a materials science approach, and the results were compared with those of mineralized cuticle. These leg tips were a non-calcified fibrous tissue of α-chitin connected to the mineralized cuticle. The tip of the second walking leg was elongated and had a pointed shape with an oval cavity at its center that was more than 1000 times larger than the pore tubes (100–350 nm) of the mineralized cuticle. It was very soft, with a hardness of 0.4 GPa, corresponding to 11–12% of the hard exocuticle and 55–57% of the soft endocuticle. The elastic modulus of 8.0 GPa obtained by nanoindentation testing was consistent with that of α-chitin fibers of shrimp shells obtained by tensile testing. These soft protrusions provide a secure grip on the surfaces of trees or rocks and protect the claw fingertips. It was concluded that the black protrusions are related to a unique ecological aspect of the coconut crab, the largest terrestrial crustacean.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: mechanical properties, nanoindentation, elemental composition, tissue structure, organic matter, α-chitin

刊行年月日: 2024-04-10

出版者: MDPI AG

掲載誌:

• Journal of Marine Science and Engineering (ISSN: 20771312) vol. 12 issue. 4 p. 639-

研究助成金:

• JSPS KAKENHI JP21H04537

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.3390/jmse12040639

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更新時刻: 2024-04-12 12:30:18 +0900

MDRでの公開時刻: 2024-04-12 12:30:19 +0900