Supplemental File 2 computed stress strain data from Hydration affects the physical and mechanical properties of baleen tissue

Baleen, an anisotropic oral filtering tissue found only in the mouth of mysticete whales and made solely of alpha-keratin, exhibits markedly differing physical and mechanical properties between dried or (as in life) hydrated states. On average baleen is 32.35% water by weight in North Atlantic right whales (<i>Eubalaena glacialis</i>) and 34.37% in bowhead whales (<i>Balaena mysticetus</i>). Baleen's wettability measured by water droplet contact angles shows that dried baleen is hydrophobic whereas hydrated baleen is highly hydrophilic. Three-point flexural bending tests of mechanical strength reveal that baleen is strong yet ductile. Dried baleen is brittle and shatters at about 20-30 N mm^-2 but hydrated baleen is less stiff; it bends with little force and absorbed water is squeezed out when force is applied. Maximum recorded stress was 4 times higher in dried (mean 14.29 N mm^-2) versus hydrated (mean 3.69 N mm^-2) baleen, and the flexural stiffness was &gt;10 times higher in dried (mean 633 N mm^-2) versus hydrated (mean 58 N mm^-2) baleen. In addition to documenting hydration's powerful effects on baleen, this study indicates that baleen is far more pliant and malleable than commonly supposed, with implications for studies of baleen's structure and function as well as its susceptibility to oil or other hydrophobic pollutants.

鲸须（Baleen）是仅存在于须鲸类（mysticete whales）口中的各向异性口腔过滤组织，仅由α-角蛋白（alpha-keratin）构成，其干燥状态与活体水合状态下的物理、力学特性存在显著差异。平均而言，北大西洋露脊鲸（<i>Eubalaena glacialis</i>）的鲸须含水率约为32.35%（以重量计），弓头鲸（<i>Balaena mysticetus</i>）的鲸须含水率则为34.37%。通过水滴接触角测得的润湿性结果显示，干燥状态的鲸须呈疏水性，而水合状态的鲸须则具有强亲水性。力学强度的三点弯曲抗弯测试表明，鲸须兼具高强度与良好延展性：干燥状态的鲸须质地较脆，断裂强度约为20~30 N·mm⁻²；水合状态的鲸须刚度更低，仅需较小外力即可使其弯曲，且受力时会挤出所吸收的水分。记录到的最大应力方面，干燥状态鲸须是水合状态的4倍（干燥组平均应力为14.29 N·mm⁻²，水合组为3.69 N·mm⁻²）；抗弯刚度则差距超过10倍，干燥组平均抗弯刚度为633 N·mm⁻²，水合组仅为58 N·mm⁻²。本研究不仅量化揭示了水分对鲸须的显著调控作用，还证实鲸须的柔韧性与延展性远超此前学界的普遍认知，该发现对于鲸须的结构与功能研究，以及其对石油或其他疏水性污染物的敏感性研究均具有重要参考价值。