Hampton Paul M
Department of Biology, University of Louisiana at Lafayette, Lafayette, Louisiana 70503, USA.
J Morphol. 2011 Dec;272(12):1435-43. doi: 10.1002/jmor.10995. Epub 2011 Jul 20.
The skull of squamates has many functions, with food acquisition and ingestion being paramount. Snakes vary interspecifically in the frequency, size, and types of prey that are consumed. Natural selection should favor phenotypes that minimize the costs of energy acquisition; therefore, trophic morphology should reflect a snake's primary prey type to enhance some aspect of feeding performance. I measured 19 cranial variables for six natricine species that vary in the frequency with which they consume frogs and fish. Both conventional and phylogenetically corrected analyses indicated that fish-eating snakes have relatively longer upper and lower jaw elements than frog-eating snakes, which tended to have broader skull components. I also compared the ratio of the in-lever to the out-lever lengths of the jaw-closing mechanism [jaw mechanical advantage (MA)] among species. Fish-eating snakes had significantly lower MAs in the jaws than did the frog-eating snakes. This result suggests that piscivores have faster closing jaws and that the jaws of frog-eating snakes have higher closing forces. Cranial morphology and the functional demands of prey capture and ingestion appear to be associated with primary prey type in natricine snakes.
有鳞目动物的头骨具有多种功能，其中获取和摄取食物最为重要。不同种类的蛇在捕食猎物的频率、大小和类型上存在差异。自然选择应青睐那些能将能量获取成本降至最低的表型；因此，食性形态应反映蛇的主要猎物类型，以提高捕食性能的某些方面。我测量了六种游蛇科物种的19个颅骨变量，这些物种捕食青蛙和鱼类的频率各不相同。传统分析和系统发育校正分析均表明，以鱼为食的蛇比以青蛙为食的蛇具有相对更长的上下颌骨，而以青蛙为食的蛇往往头骨组成部分更宽。我还比较了不同物种间下颌闭合机制的内杠杆长度与外杠杆长度之比[下颌机械优势（MA）]。以鱼为食的蛇的下颌MA显著低于以青蛙为食的蛇。这一结果表明，食鱼蛇的下颌闭合速度更快，而食蛙蛇的下颌具有更大的闭合力。颅骨形态以及猎物捕获和摄取的功能需求似乎与游蛇科蛇类的主要猎物类型有关。
