Müller Ulrike K, van Leeuwen Johan L
Wageningen University, Experimental Zoology Group, Marijkeweg 40, 6709 PG Wageningen, The Netherlands.
J Exp Biol. 2004 Feb;207(Pt 5):853-68. doi: 10.1242/jeb.00821.
Fish larvae, like most adult fish, undulate their bodies to propel themselves. A detailed kinematic study of the larval body wave is a prerequisite to formulate a set of functional requirements that the locomotor system must fulfil to generate the observed swimming kinematics. Lateral displacement and curvature profiles were obtained for zebrafish (Danio rerio) larvae at 2-21 days post-fertilisation for three swimming behaviours (cyclic swimming, slow starts and fast startle responses) using high-speed video. During cyclic swimming, fish larvae maintain tail beat frequencies of up to 100 Hz. The corresponding longitudinal strains, estimated from the peak curvatures of the midline, reach up to 0.19 in superficial tissue. The strain rate can reach 120 s(-1). The wave of curvature travels along the body at a near-constant rate. Posterior to the stiff head, body-length-specific curvature is high and rises gently along the entire trunk to a maximum value of 6. Burst-and-coast swimming generates similar peak curvatures to cyclic swimming, but curvature rises more steeply from head to tail. Fish larvae exhibit phase shifts of 57-63 degrees between the wave of lateral displacement and the wave of curvature, resulting in a 1:1.2 ratio of body wave length to curvature wave length. During C-starts, muscle strain can reach 0.19 and superficial longitudinal strain rates approach 30 s(-1). Fish larvae do not initiate their escape response with a standing wave of curvature, although their C-starts approach a standing wave as the larvae grow older. The performance demands derived from swimming kinematics suggest that larval axial muscles have very short contraction cycles (10 ms), experience considerable strains (up to 0.2) and strain rates (up to 30 s(-1) in white muscle fibres) yet are able to power swimming for several seconds.
鱼类幼体与大多数成年鱼类一样，通过身体摆动来推动自身前进。对幼体身体波动进行详细的运动学研究，是制定运动系统为产生所观察到的游泳运动学必须满足的一系列功能要求的前提条件。利用高速视频，获取了受精后2至21天的斑马鱼（Danio rerio）幼体在三种游泳行为（循环游泳、慢启动和快速惊吓反应）下的横向位移和曲率剖面。在循环游泳过程中，鱼类幼体保持高达100赫兹的尾鳍摆动频率。从中线峰值曲率估计的相应纵向应变，在表层组织中可达0.19。应变率可达120秒⁻¹。曲率波以近乎恒定的速率沿身体传播。在坚硬的头部后方，特定体长的曲率很高，并沿整个躯干平缓上升至最大值6。爆发-滑行游泳产生的峰值曲率与循环游泳相似，但曲率从头部到尾部上升得更陡。鱼类幼体在横向位移波和曲率波之间表现出57至63度的相位差，导致身体波长与曲率波长的比例为1:1.2。在C型启动过程中，肌肉应变可达0.19，表层纵向应变率接近30秒⁻¹。鱼类幼体不会以曲率驻波启动逃避反应，尽管随着幼体长大，它们的C型启动接近驻波。从游泳运动学得出的性能要求表明，幼体轴向肌肉具有非常短的收缩周期（10毫秒），经历相当大的应变（高达0.2）和应变率（白色肌纤维中高达30秒⁻¹），但仍能为游泳提供数秒的动力。
