Jastrebsky Rachel A, Bartol Ian K, Krueger Paul S
Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA
Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA.
J Exp Biol. 2016 May 1;219(Pt 9):1317-26. doi: 10.1242/jeb.126839. Epub 2016 Mar 4.
Although steady swimming has received considerable attention in prior studies, unsteady swimming movements represent a larger portion of many aquatic animals' locomotive repertoire and have not been examined extensively. Squids and cuttlefishes are cephalopods with unique muscular hydrostat-driven, dual-mode propulsive systems involving paired fins and a pulsed jet. These animals exhibit a wide range of swimming behavior, but turning performance has not been examined quantitatively. Brief squid, Lolliguncula brevis, and dwarf cuttlefish, Sepia bandensis, were filmed during turns using high-speed cameras. Kinematic features were tracked, including the length-specific radius of the turn (R/L), a measure of maneuverability, and angular velocity (ω), a measure of agility. Both L. brevis and S. bandensis demonstrated high maneuverability, with (R/L)min values of 3.4×10(-3)±5.9×10(-4) and 1.2×10(-3)±4.7×10(-4) (mean±s.e.m.), respectively, which are the lowest measures of R/L reported for any aquatic taxa. Lolliguncula brevis exhibited higher agility than S. bandensis (ωa,max=725.8 versus 485.0 deg s(-1)), and both cephalopods have intermediate agility when compared with flexible-bodied and rigid-bodied nekton of similar size, reflecting their hybrid body architecture. In L. brevis, jet flows were the principal driver of angular velocity. Asymmetric fin motions played a reduced role, and arm wrapping increased turning performance to varying degrees depending on the species. This study indicates that coordination between the jet and fins is important for turning performance, with L. brevis achieving faster turns than S. bandensis and S. bandensis achieving tighter, more controlled turns than L. brevis.
尽管稳定游泳在先前的研究中受到了相当多的关注，但不稳定的游泳动作在许多水生动物的运动技能中占比更大，且尚未得到广泛研究。鱿鱼和乌贼是头足类动物，具有独特的由肌肉静水骨骼驱动的双模式推进系统，该系统涉及成对的鳍和脉冲式喷射。这些动物表现出广泛的游泳行为，但转弯性能尚未得到定量研究。使用高速摄像机在短鳍鱿鱼（Lolliguncula brevis）和侏儒乌贼（Sepia bandensis）转弯过程中进行拍摄。追踪了运动学特征，包括转弯的长度特定半径（R/L），这是一种机动性的度量，以及角速度（ω），这是一种敏捷性的度量。短鳍鱿鱼和侏儒乌贼都表现出高机动性，其（R/L）最小值分别为3.4×10(-3)±5.9×10(-4)和1.2×10(-3)±4.7×10(-4)（平均值±标准误），这是所有水生分类群中报道的最低R/L值。短鳍鱿鱼比侏儒乌贼表现出更高的敏捷性（ωa,max = 725.8对485.0度·秒(-1)），并且与类似大小的柔性身体和刚性身体的游泳动物相比，这两种头足类动物都具有中等敏捷性，这反映了它们混合的身体结构。在短鳍鱿鱼中，喷射流是角速度的主要驱动因素。不对称的鳍运动起的作用较小，并且触腕缠绕根据物种不同在不同程度上提高了转弯性能。这项研究表明，喷射和鳍之间的协调对于转弯性能很重要，短鳍鱿鱼比侏儒乌贼转弯更快，而侏儒乌贼比短鳍鱿鱼转弯更紧凑、更可控。
