Biomechanical determinants of bite force dimorphism in Cyclommatus metallifer stag beetles
Biomechanical determinants of bite force dimorphism in Cyclommatus metallifer stag beetles
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DOI：
10.1242/jeb.091744
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发表时间：
2014-04-01
影响因子：
2.8
通讯作者：
Aerts, Peter
中科院分区：
文献类型：
--
作者：
Goyens, Jana;Dirckx, Joris;Aerts, Peter
在锹虫科（Lucanidae）中，雄性通过性选择与雌性分化。雄性用扩大的下颌互相争夺交配机会。众所周知，拥有较大战斗器械的人更有利于赢得雄性与雄性的战斗，但尚不清楚雄性锹虫在战斗中抓住和举起对手时是否也需要产生高咬合力。我们发现，雄性雄鹿甲虫的咬合力是雌性的三倍。考虑到战斗的壮观性质，这并不完全出乎意料，但考虑到用长下颌（长杠杆）实现这一目标的难度，更令人印象深刻。我们的研究结果表明，男性内在肌肉力量并没有增加来实现这一目标。然而，形态学分析表明，男性较长的下颌输出杠杆被延长的输入杠杆（因此头部的前侧更宽）所补偿。男性咬合力能力的过剩是通过扩大下颌骨较近的肌肉来实现的，同时整体肌肉力的方向保持最佳。为了实现确保雄性成功繁殖所需的强力咬合，雄性头部的尺寸和形状适合长输入杆和大肌肉。因此，整个头部应该被视为男性骨架的一个组成部分。
In the stag beetle family (Lucanidae), males have diverged from females by sexual selection. The males fight each other for mating opportunities with their enlarged mandibles. It is known that owners of larger fighting apparatuses are favoured to win the male-male fights, but it was unclear whether male stag beetles also need to produce high bite forces while grabbing and lifting opponents in fights. We show that male Cyclommatus metallifer stag beetles bite three times as forcefully as females. This is not entirely unexpected given the spectacular nature of the fights, but all the more impressive given the difficulty of achieving this with their long mandibles (long levers). Our results suggest no increase in male intrinsic muscle strength to accomplish this. However, morphological analyses show that the long mandibular output levers in males are compensated by elongated input levers (and thus a wider anterior side of the head). The surplus of male bite force capability is realized by enlargement of the closer muscles of the mandibles, while overall muscle force direction remained optimal. To enable the forceful bites required to ensure male reproductive success, male head size and shape are adapted for long input levers and large muscles. Therefore, the entire head should be regarded as an integral part of male armature.