Functional implications of supercontracting muscle in the chameleon tongue retractors.
Functional implications of supercontracting muscle in the chameleon tongue retractors.
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发表时间：
2001-11
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通讯作者：
Anthony Herrel;J. Meyers;Peter Aerts;K. Nishikawa
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作者：
Anthony Herrel;J. Meyers;Peter Aerts;K. Nishikawa
变色龙使用蜥蜴中独一无二的弹道舌头投影机制捕捉猎物。在捕获猎物的过程中，舌头可以伸出两个全身的长度，并可以延伸到其静止长度的600%。变色龙是埋伏的捕食者，很少进食，捕食的猎物相对较大。舌头的极端伸长(六倍)，以及需要能够在距离嘴的任何给定距离处缩回相当重的猎物，都可能对舌头缩回肌造成限制。这里检查的数据表明，在很大的投影距离范围内，体内牵引力的产生几乎是恒定的。肌肉生理学和舌牵张肌超微结构的检查表明，这是(I)舌骨主动收缩，(Ii)舌最大伸展时肌丝大量重叠和(Iii)舌拉肌超收缩特性的结果。我们认为，变色龙的舌部牵引肌可能进化出了超收缩特性，从而能够在很大范围的舌头投射距离上产生相当大的力量。这使得变色龙能够在其复杂的三维栖息地成功地从不同的距离撤回甚至大型猎物。
Chameleons capture prey items using a ballistic tongue projection mechanism that is unique among lizards. During prey capture, the tongue can be projected up to two full body lengths and may extend up to 600 % of its resting length. Being ambush predators, chameleons eat infrequently and take relatively large prey. The extreme tongue elongation (sixfold) and the need to be able to retract fairly heavy prey at any given distance from the mouth are likely to place constraints on the tongue retractor muscles. The data examined here show that in vivo retractor force production is almost constant for a wide range of projection distances. An examination of muscle physiology and of the ultrastructure of the tongue retractor muscle shows that this is the result (i) of active hyoid retraction, (ii) of large muscle filament overlap at maximal tongue extension and (iii) of the supercontractile properties of the tongue retractor muscles. We suggest that the chameleon tongue retractor muscles may have evolved supercontractile properties to enable a substantial force to be produced over a wide range of tongue projection distances. This enables chameleons successfully to retract even large prey from a variety of distances in their complex three-dimensional habitat.