Institut für Zoologie der Universität Bonn, Poppelsdorfer Schloss, 53115 Bonn, Germany.
Arthropod Struct Dev. 2013 Mar;42(2):135-42. doi: 10.1016/j.asd.2012.11.001. Epub 2012 Nov 23.
The pyrophilous Australian "fire-beetle"Merimna atrata approaches forest fires and possesses abdominal infrared (IR) organs. Each round IR organ is centrally innervated by a sensory complex showing two different units: one thermoreceptive multipolar neuron and one mechanosensitive chordotonal organ (CO) consisting of two scolopidia. We investigated the CO and found that the scolopidia are mononematic (the scolopale cap remains below the cuticle) and monodynal (one sensory cell per scolopidium). The dendrites of the scolopidia extend anteriorly and are attached by their caps to the cuticle about in the middle of the absorbing area. Structural features at the site of innervation suggest that the CO measures minute thermal deformations caused by IR absorption. Therefore, an additional photomechanic component which has been described for the IR receptors of pyrophilous jewel beetles of the genus Melanophila can be proposed for the IR organ of Merimna. Because scolopidia can measure displacements in the subnanometer range, the CO may enhance the sensitivity of the IR organ. The sensory complex of the Merimna IR organ shows the same units and similar cuticular modifications as the tympanal organs of some noctuid moths. Therefore, a parallel evolution of insect ears and the Merimna IR organ is discussed.
嗜火的澳大利亚“火甲虫”Merimna atrata 接近森林火灾，并拥有腹部红外（IR）器官。每个圆形的 IR 器官都由一个感觉复合物中央神经支配，该复合物显示出两种不同的单位：一个热敏多极神经元和一个由两个刺状感器组成的机械敏感的音叉器官（CO）。我们研究了 CO，发现刺状感器是单轴的（刺状感器帽仍在角质层下）和单原的（每个刺状感器一个感觉细胞）。刺状感器的树突向前延伸，并通过其帽附着在角质层上，大约在吸收区域的中间。神经支配部位的结构特征表明，CO 测量由 IR 吸收引起的微小热变形。因此，可以为嗜火的金龟子属 Melanophila 的 IR 感受器描述一个额外的光机械组件，这个组件可以被提议用于 Merimna 的 IR 器官。由于刺状感器可以测量亚纳米级的位移，因此 CO 可能会提高 IR 器官的灵敏度。Merimna 的 IR 器官的感觉复合物显示出与某些夜蛾科飞蛾的鼓膜器官相同的单位和类似的角质层修饰。因此，讨论了昆虫耳朵和 Merimna 的 IR 器官的平行进化。
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