O'Reilly S R, Nishikawa K C
Department of Biological Sciences, Northern Arizona University, Flagstaff 86011-5640, USA.
J Exp Zool. 1995 Nov 1;273(4):282-96. doi: 10.1002/jez.1402730403.
Recent studies have used muscle denervation experiments to examine the function of muscles during feeding in frogs. By comparing the results of denervation experiments among taxa, it is possible to identify evolutionary changes in muscle function. The purpose of this study was to examine the function of jaw and tongue muscles during prey capture in Spea multiplicata, a representative of the superorder Mesobatrachia. All members of this group possess a disjunct hyoid apparatus. We predicted that Spea would possess a novel mechanism of tongue protraction on the basis of its hyoid morphology. High-speed video motion analysis and muscle denervation were used to study the feeding behavior and mechanism of tongue protraction in Spea. Although Spea possesses a relatively long tongue, its feeding behavior is similar to that of short-tongued frogs of similar body size. Denervation of the m. submentalis had no effect on feeding behavior. When the m. geniohyoideus was denervated, the tongue pad was raised and moved forward slightly, but did not leave the mouth. When the m. genioglossus was denervated, the tongue pad was raised slightly, but no forward movement of the tongue occurred. A similar result was obtained after the mm. genioglossus and geniohyoideus were denervated simultaneously. Thus, both the mm. genioglossus and geniohyoideus are necessary for normal tongue protraction in Spea. In contrast, only the m. genioglossus is necessary for normal tongue protraction in archaeobatrachians and neobatrachians. We hypothesize that the disjunct hyoid is responsible for the greater role of hyoid movement during feeding in mesobatrachians.
最近的研究利用肌肉去神经支配实验来研究青蛙进食时肌肉的功能。通过比较不同类群去神经支配实验的结果，有可能识别肌肉功能的进化变化。本研究的目的是研究多斑锄足蟾（中蛙亚目代表物种）捕食猎物时颌部和舌部肌肉的功能。该类群的所有成员都拥有分离的舌骨装置。我们预测，基于其舌骨形态，多斑锄足蟾会拥有一种新颖的伸舌机制。利用高速视频运动分析和肌肉去神经支配来研究多斑锄足蟾的进食行为和伸舌机制。尽管多斑锄足蟾拥有相对较长的舌头，但其进食行为与体型相似的短舌蛙类似。颏下肌去神经支配对进食行为没有影响。当颏舌骨肌去神经支配时，舌垫抬起并稍微向前移动，但未离开口腔。当舌肌去神经支配时，舌垫稍微抬起，但舌头没有向前移动。舌肌和颏舌骨肌同时去神经支配后也得到了类似结果。因此，舌肌和颏舌骨肌对于多斑锄足蟾正常的伸舌都是必需的。相比之下，在古蛙亚目和新蛙亚目动物中，正常伸舌仅需要舌肌。我们推测，分离的舌骨是中蛙亚目动物进食时舌骨运动发挥更大作用的原因。
