Sutton G P, Macknin J B, Gartman S S, Sunny G P, Beer R D, Crago P E, Neustadter D M, Chiel H J
Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106-7080, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2004 Jun;190(6):501-14. doi: 10.1007/s00359-004-0517-4. Epub 2004 Apr 20.
Swallowing and biting responses in the marine mollusk Aplysia are both mediated by a cyclical alternation of protraction and retraction movements of the grasping structure, the radula and underlying odontophore, within the feeding apparatus of the animal, the buccal mass. In vivo observations demonstrate that Aplysia biting is associated with strong protractions and rapid initial retractions, whereas Aplysia swallowing is associated with weaker protractions and slower initial retractions. During biting, the musculature joining the radula/odontophore to the buccal mass (termed the "hinge") is stretched more than in swallowing. To test the hypothesis that stretch of the hinge might contribute to rapid retractions observed in biting, we analyzed the hinge's passive properties. During biting, the hinge is stretched sufficiently to assist retraction. In contrast, during swallowing, the hinge is not stretched sufficiently for its passive forces to assist retraction, because the odontophore's anterior movement is smaller than during biting. A quantitative model demonstrated that steady-state passive forces were sufficient to generate the retraction movements observed during biting. Experimental measures of the relative magnitude of the hinge's active and passive forces at the protraction displacements of biting suggest that passive forces are at least a third of the total force.
海洋软体动物海兔的吞咽和咬食反应均由抓取结构（齿舌及其下方的齿舌载体）在动物进食器官（口腔团块）内的周期性伸展和收缩运动介导。活体观察表明，海兔咬食与强烈的伸展和快速的初始收缩有关，而海兔吞咽则与较弱的伸展和较慢的初始收缩有关。在咬食过程中，连接齿舌/齿舌载体与口腔团块的肌肉组织（称为“铰链”）比吞咽时伸展得更多。为了验证铰链伸展可能有助于咬食时观察到的快速收缩这一假设，我们分析了铰链的被动特性。在咬食过程中，铰链伸展得足够程度以协助收缩。相比之下，在吞咽过程中，铰链伸展程度不足以使其被动力协助收缩，因为齿舌载体的向前运动比咬食时小。一个定量模型表明，稳态被动力足以产生咬食时观察到的收缩运动。在咬食伸展位移时对铰链主动力和被动力相对大小的实验测量表明，被动力至少占总力的三分之一。
