Using the axial skeleton as armor: mechanical behavior of sea turtle carapaces throughout ontogeny.

IF 2.8 2区 生物学 Q2 BIOLOGY
Journal of Experimental Biology Pub Date : 2025-04-01 Epub Date: 2025-04-09 DOI:10.1242/jeb.249959
Ivana J Lezcano, Jeanette Wyneken, Marianne E Porter
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Abstract

The shells of turtles serve as protection, yet shell shape and natural history widely vary among turtles. Here, we identify the mechanical behavior that provides marine turtles, species characterized with fusiform shells, with biomechanical strength and resilience. The multi-layered carapacial bone structure seemingly serves a protective role for the muscles, nerves and viscera it houses. What are the shell's material properties that provide protection? Most previous work has focused on non-marine turtles, which differ in natural history and shell morphology from marine species. We measured carapacial mechanical behavior of green turtle (Chelonia mydas), loggerhead (Caretta caretta) and Kemp's ridleys (Lepidochelys kempii) across a range of body sizes in juveniles, subadults and adults. Carapace samples were tested using quasi-static compression to quantify stiffness (Young's modulus), yield strength and toughness. The mechanical characteristics of marine turtle shells are grossly akin to those of other turtles and driven by the bone's sandwich structure. Yet, the material properties indicate that marine turtle shells are less stiff and strong than those of their freshwater and terrestrial counterparts. We hypothesize that increased flexibility of the shell may reflect tradeoffs for life that include experiencing pressure from diving somewhat deeply in marine environments. Shell material properties also differ among species and ontogenetically. Green turtles have the stiffest, strongest and toughest shells while loggerhead carapaces are the most compliant. Stiffness and yield strength show positive relationships with body size which are most pronounced in green turtles and Kemp's ridleys. Phylogenetic histories and ecological differences likely drive this interspecific variation.

把轴骨架当作盔甲:海龟甲壳在整个个体发育过程中的机械行为。
海龟的壳起到保护作用,但海龟的壳形状和自然历史差异很大。在这里,我们确定了为具有梭状壳的海龟提供生物力学强度和弹性的力学行为。多层甲骨结构似乎对它所容纳的肌肉、神经和内脏起着保护作用。提供保护的外壳材料特性是什么?大多数以前的工作都集中在自然历史和壳形态与海洋物种不同的非海洋海龟上。我们测量了不同体型的绿龟(Chelonia mydas)、红海龟(Caretta Caretta)和肯普雷氏龟(Lepidochelys kempii)幼龟、亚成龟和成龟的腕部力学行为。外壳样品使用准静态压缩进行测试,以量化刚度(杨氏模量)、屈服强度和韧性。海龟壳的机械特性与其他海龟非常相似,是由骨头的三明治结构驱动的。然而,材料特性表明,海龟壳的硬度和强度不如淡水海龟和陆地海龟。我们假设,壳的灵活性增加可能反映了生命的权衡,包括在海洋环境中深度潜水所承受的压力。壳材料性质在物种和个体间也存在差异。绿海龟的壳最硬、最结实、最坚硬,而红海龟的甲壳最柔顺。刚度和屈服强度与体型呈正相关,在绿海龟和坎普雷德利中最为明显。系统发育历史和生态差异可能驱动这种种间变异。
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来源期刊
CiteScore
5.50
自引率
10.70%
发文量
494
审稿时长
1 months
期刊介绍: Journal of Experimental Biology is the leading primary research journal in comparative physiology and publishes papers on the form and function of living organisms at all levels of biological organisation, from the molecular and subcellular to the integrated whole animal.
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