Kuenzi F M, Carew T J
Department of Biology, Yale University, New Haven, CT 06520.
J Exp Biol. 1994 Oct;195:35-51. doi: 10.1242/jeb.195.1.35.
Searching is an important component of several types of goal-directed behaviour. In soft-bodied animals, searching behaviour can appear quite complex because the range of body movement is not constrained by joints, limbs or muscles with discrete areas of origin and insertion. In addition, animals exhibiting this type of behaviour utilize their maximum freedom of movement. In this paper, we describe the head-waving searching behaviour of the sea hare Aplysia californica by characterizing patterns of movements and the changes in body shape that underlie these movements. A bout of head waving consists of a series of discrete movements separated by pauses. Each discrete movement lasts 4-10s and is directed either horizontally or vertically with respect to stationary part of the animal. Large movements, such as bending from the extreme right to the extreme left, consist of a series of these shorter movements separated by pauses lasting 1-2s. In all head-waving movements, the transverse axis of the head is kept relatively parallel with the substratum. Thus, vertical movements require only bending of the body, whereas horizontal movements require twisting of the body, particularly when the posture is more erect. During head waving, the anterior two-thirds of the body is free to move, but most of the bending occurs immediately posterior to the head region. There is no periodicity of movements within a bout of head waving, although isolated instances of repeated movements are sometimes observed. Therefore, although the individual movements during head waving are relatively simple, the absence of a patterned sequence accounts for the complexity of the overall behaviour. These observations both constrain models of the neural organization of head waving and provide criteria for categorizing head-waving movements in further behavioural and physiological studies.
搜索是几种目标导向行为的重要组成部分。在软体动物中，搜索行为可能显得相当复杂，因为身体运动的范围不受具有离散起始和插入区域的关节、肢体或肌肉的限制。此外，表现出这种行为类型的动物会充分利用其最大的运动自由度。在本文中，我们通过描述运动模式以及这些运动背后的身体形状变化，来阐述海兔加州海兔的头部摆动搜索行为。一阵头部摆动由一系列被暂停隔开的离散运动组成。每个离散运动持续4 - 10秒，相对于动物的静止部分，运动方向要么是水平的，要么是垂直的。大的运动，比如从最右端弯曲到最左端，由一系列这些较短的运动组成，这些运动被持续1 - 2秒的暂停隔开。在所有头部摆动运动中，头部的横轴与基质保持相对平行。因此，垂直运动只需要身体弯曲，而水平运动需要身体扭转，尤其是当姿势更直立时。在头部摆动期间，身体的前三分之二可以自由移动，但大部分弯曲发生在头部区域后方紧邻的位置。在一阵头部摆动中，运动没有周期性，尽管有时会观察到孤立的重复运动实例。因此，尽管头部摆动期间的单个运动相对简单，但缺乏有规律的序列导致了整体行为的复杂性。这些观察结果既限制了头部摆动神经组织模型，也为在进一步的行为和生理学研究中对头部摆动运动进行分类提供了标准。
