Comparative and developmental functional morphology of the jaws of living and fossil gars (Actinopterygii: Lepisosteidae)
Comparative and developmental functional morphology of the jaws of living and fossil gars (Actinopterygii: Lepisosteidae)
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DOI：
10.1002/jmor.10293
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发表时间：
2006-09-01
影响因子：
1.5
通讯作者：
Westneat, Mark W.
中科院分区：
文献类型：
--
作者：
Kammerer, Christian F.;Grande, Lance;Westneat, Mark W.
加尔斯（Ginglymodi：Lepisosteidae）的进食机制以头颅抬高和下颌旋转为特征，但头颅运动很少。雀鳝的下颚有许多尖锐的长牙，用来捕捉躲避的猎物。它们的下颌骨从相对较短到极长不等，这取决于物种。根据肌肉通过一阶或三阶杠杆施加力的简单力学模型，假设下颌长度和杠杆尺寸会影响进食过程中的力和运动的生物力学。一个形态测量协议被用来测量颌骨结构的7个活的和5个化石物种的雀鳝和这些数据被用来计算机械优势（力传递的措施）的开放和关闭的下颌骨。加尔斯被发现具有低的机械优势（MA）和高传输的运动，虽然加尔斯占据了一系列的生物力学状态的连续的力与速度传输。长鼻雀鳝，Lepisosteus osseus，有一个最低的下巴关闭MA（0.05）曾经在鱼类中测量。此外，还计算了一个发育系列（从取食幼虫到成虫）的种内杠杆力学。骨突和匙突下颌骨MA的特征个体发育曲线，在幼虫和少年之间的MA大幅度下降，随后在成人生长期间稳定增加。这条曲线与猎物类型的变化相关，小，强壮的下巴主要以甲壳类动物和昆虫为食，所有物种的大，长下巴的个体主要以食鱼为主。功能重要的形态计量学的主成分分析表明，几种雀鳝占据不同的区域的功能形态空间。一些化石雀鳝物种也被放置在功能形态空间使用这种方法。
The feeding mechanism of gars (Ginglymodi : Lepisosteidae) is characterized by cranial elevation and lower jaw rotation but minimal cranial kinesis. Gar jaws have numerous, sharply pointed, elongate teeth for capture of evasive prey. Their mandibles range from relatively short to extremely long depending on the species. Jaw length and lever dimensions were hypothesized to affect the biomechanics of force and motion during feeding, according to simple mechanical models of muscles exerting force through first- or third-order levers. A morphometric protocol was used to measure the jaw structure of seven living and five fossil species of gar and these data were used to calculate the mechanical advantage (a measure of force transmission) for both opening and closing of the mandible. Gars were found to possess low mechanical advantage (MA) and high transmission of motion, although gars occupy a range of biomechanical states across the continuum of force vs. velocity transmission. The long-nose gar, Lepisosteus osseus, has one of the lowest jaw closing MAs (0.05) ever measured in fishes. Intraspecific lever mechanics were also calculated for a developmental series (from feeding larvae to adults) of L. osseus and Atractosteus spatula. A characteristic ontogenetic curve in MA of the lower jaw was obtained, with a large decrease in MA between larva and juvenile, followed by a steady increase during adult growth. This curve correlates with a change in prey type, with the small, robust-jawed individuals feeding mainly on crustaceans and insects and the large, long-jawed individuals of all species becoming mainly piscivorous. Principal components analysis of functionally important morphometrics shows that several gar species occupy different regions of functional morphospace. Some fossil gar species are also placed within functional morphospace using this approach.