Departamento de Ingeniería Mecánica, Universidad de Santiago de Chile (USACH), Av. Bernardo O'Higgins 3363, Santiago de Chile, Chile.
Centro de Investigación e Innovación para el Cambio Climático (CiiCC), Universidad Santo Tomás, Av. Ejército Libertador 146, Santiago de Chile, Chile.
Sci Rep. 2022 Jan 13;12(1):710. doi: 10.1038/s41598-021-04414-1.
Mollusks have developed a broad diversity of shelled structures to protect against challenges imposed by biological interactions(e.g., predation) and constraints (e.g., [Formula: see text]-induced ocean acidification and wave-forces). Although the study of shell biomechanical properties with nacreous microstructure has provided understanding about the role of shell integrity and functionality on mollusk performance and survival, there are no studies, to our knowledge, that delve into the variability of these properties during the mollusk ontogeny, between both shells of bivalves or across the shell length. In this study, using as a model the intertidal mussel Perumytilus purpuratus to obtain, for the first time, the mechanical properties of its shells with nacreous microstructure; we perform uniaxial compression tests oriented in three orthogonal axes corresponding to the orthotropic directions of the shell material behavior (thickness, longitudinal, and transversal). Thus, we evaluated whether the shell material's stress and strain strength and elastic modulus showed differences in mechanical behavior in mussels of different sizes, between valves, and across the shell length. Our results showed that the biomechanical properties of the material building the P. purpuratus shells are symmetrical in both valves and homogeneous across the shell length. However, uniaxial compression tests performed across the shell thickness showed that biomechanical performance depends on the shell size (aging); and that mechanical properties such as the elastic modulus, maximum stress, and strain become degraded during ontogeny. SEM observations evidenced that compression induced a tortuous fracture with a delamination effect on the aragonite mineralogical structure of the shell. Findings suggest that P. purpuratus may become vulnerable to durophagous predators and wave forces in older stages, with implications in mussel beds ecology and biodiversity of intertidal habitats.
软体动物已经发展出了广泛的壳结构多样性，以抵御生物相互作用（例如捕食）和限制（例如，[Formula: see text]诱导的海洋酸化和波浪力）带来的挑战。尽管对具有珍珠层微观结构的贝壳生物力学特性的研究提供了关于贝壳完整性和功能对软体动物性能和生存的作用的理解，但据我们所知，没有研究深入探讨这些特性在软体动物个体发育过程中的变化，也没有研究这些特性在双壳贝类的两个贝壳之间或沿贝壳长度方向的变化。在这项研究中，我们以潮间带贻贝 Perumytilus purpuratus 为模型，首次获得了其具有珍珠层微观结构的贝壳的机械性能；我们进行了单轴压缩测试，测试方向为与贝壳材料行为各向异性方向（厚度、纵向和横向）对应的三个正交轴。因此，我们评估了贝壳材料的应力和应变强度以及弹性模量是否在不同大小的贻贝、贝壳之间以及贝壳长度方向上表现出不同的机械行为。我们的结果表明，构建 P. purpuratus 贝壳的材料的生物力学特性在两个贝壳之间是对称的，并且在贝壳长度方向上是均匀的。然而，跨贝壳厚度进行的单轴压缩测试表明，生物力学性能取决于贝壳的大小（年龄）；并且弹性模量、最大应力和应变等机械性能在个体发育过程中会退化。SEM 观察表明，压缩会导致贝壳的文石矿物结构发生扭曲断裂，并产生分层效应。研究结果表明，P. purpuratus 在老年阶段可能更容易受到咀嚼型捕食者和波浪力的影响，这对潮间带栖息地的贻贝床生态和生物多样性有影响。
