The opercular mouth-opening mechanism of largemouth bass functions as a 3D four-bar linkage with three degrees of freedom
The opercular mouth-opening mechanism of largemouth bass functions as a 3D four-bar linkage with three degrees of freedom
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DOI：
10.1242/jeb.159079
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发表时间：
2017-12-15
影响因子：
2.8
通讯作者：
Brainerd, Elizabeth L.
中科院分区：
文献类型：
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作者：
Olsen, Aaron M.;Camp, Ariel L.;Brainerd, Elizabeth L.
平面单自由度（1-DoF）四杆机构是理解众多生物力学系统的功能、性能和演化的重要模型。一个这样的系统是鱼类的眼机制，它被认为是像一个四杆连杆一样的功能来抑制下颚。虽然解剖学和行为学观察表明存在某种形式的机械耦合，但之前将眼机制建模为平面四杆的尝试，相对于观察到的运动学，一直产生较差的模型拟合。利用新开发的开源机构拟合软件，我们将具有不同自由度的多个三维（3D）四杆模型拟合到大口黑鲈的体内运动学中，以测试眼机构是否具有具有一个或多个自由度的三维四杆。我们检查了连杆位置误差、连杆旋转误差和输出与输入连杆旋转的比率，以确定两种不同变化水平下的最佳拟合模型：针对每个进给打击和来自同一个体的所有打击。三维三自由度四杆机构是最适合眼机构的模型，连杆旋转误差小于5%。我们还发现，在每次打击的水平和跨越多次打击，眼机构以多个自由度移动。这些结果表明，主动电机控制可能需要通过轴向肌肉将力输入到机构中，并实现特定的张嘴轨迹。我们的研究结果还扩展了四杆模型在模拟生物力学系统中的多功能性，并将其应用范围扩展到平面或单自由度系统之外。
The planar, one degree of freedom (1-DoF) four-bar linkage is an important model for understanding the function, performance and evolution of numerous biomechanical systems. One such system is the opercular mechanism in fishes, which is thought to function like a four-bar linkage to depress the lower jaw. While anatomical and behavioral observations suggest some form of mechanical coupling, previous attempts to model the opercular mechanism as a planar four-bar have consistently produced poor model fits relative to observed kinematics. Using newly developed, open source mechanism fitting software, we fitted multiple three-dimensional (3D) four-bar models with varying DoF to in vivo kinematics in largemouth bass to test whether the opercular mechanism functions instead as a 3D four-bar with one or more DoF. We examined link position error, link rotation error and the ratio of output to input link rotation to identify a best-fit model at two different levels of variation: for each feeding strike and across all strikes from the same individual. A 3D, 3-DoF four-bar linkage was the best-fit model for the opercular mechanism, achieving link rotational errors of less than 5%. We also found that the opercular mechanism moves with multiple degrees of freedom at the level of each strike and across multiple strikes. These results suggest that active motor control may be needed to direct the force input to the mechanism by the axial muscles and achieve a particular mouth-opening trajectory. Our results also expand the versatility of four-bar models in simulating biomechanical systems and extend their utility beyond planar or single-DoF systems.