Saif Nasif Bin, Guilani Ramin J A, Ramezanpour Shayan, Toofani Arman, Eraghi Sepehr H, Goss Geoff, Lin Chung-Ping, Gorb Stanislav, Rajabi Hamed
Mechanical Intelligence (MI) Research Group, Bioscience and Bioengineering Research Centre, London South Bank University (LSBU), London SE1 0AA, United Kingdom.
Centre for Industrial Mechanics, Department of Mechanical and Electrical Engineering, University of Southern Denmark (SDU ), Sønderborg 6400, Denmark.
PNAS Nexus. 2025 Jun 20;4(7):pgaf205. doi: 10.1093/pnasnexus/pgaf205. eCollection 2025 Jul.
Stag beetle mandibles exhibit remarkable interspecific variation, reflecting adaptations for species-specific combat strategies. This study investigates the functional basis of this diversity by analyzing the mandibles of five species using high-resolution finite-element analysis and geometric morphometrics. We simulated four distinct combat maneuvers-squeezing, holding, lifting, and twisting-and quantified mechanical performance via stress and strain energy, under standardized conditions. Principal component analysis of mandible morphology revealed two major axes of variation linked to shape and tip complexity. Our results show that certain mandible designs exhibit superior mechanical efficiency in maneuvers typical of their known fighting behavior, particularly in squeezing and twisting, suggesting functional specialization. However, mismatches also emerged, indicating latent mechanical capabilities or limitations in behavioral data. An exploratory correlation analysis highlights links between tip complexity (principal component 2) and biomechanical performance. Lifting performance was almost consistent across species, suggesting that whole-body kinematics may dominate this action. This work offers new insights into the evolution of animal weaponry by demonstrating that mandible shape in stag beetles is often aligned with species-typical combat strategies but not strictly constrained by observed behavior. It further provides a quantitative framework for linking morphology and mechanical performance in biomechanically complex systems.
锹甲的下颚表现出显著的种间差异，这反映了对特定物种战斗策略的适应性。本研究通过使用高分辨率有限元分析和几何形态计量学分析五个物种的下颚，来探究这种多样性的功能基础。我们模拟了四种不同的战斗动作——挤压、抓握、抬起和扭转——并在标准化条件下通过应力和应变能对机械性能进行量化。下颚形态的主成分分析揭示了与形状和尖端复杂性相关的两个主要变异轴。我们的结果表明，某些下颚设计在其已知战斗行为典型的动作中表现出卓越的机械效率，特别是在挤压和扭转动作中，这表明存在功能特化。然而，也出现了不匹配的情况，这表明行为数据中存在潜在的机械能力或限制。一项探索性相关分析突出了尖端复杂性（主成分2）与生物力学性能之间的联系。抬起性能在不同物种间几乎一致，这表明全身运动学可能主导了这个动作。这项工作通过证明锹甲的下颚形状通常与物种典型的战斗策略相一致，但并不严格受观察到的行为的限制，为动物武器装备提供了新的见解。它还为在生物力学复杂系统中将形态与机械性能联系起来提供了一个定量框架。
