Gibbs Brendan J, Akanyeti Otar, Liao James C
Department of Biology, The Whitney Laboratory for Marine Bioscience, University of Florida, St Augustine, FL 32080, USA.
Department of Computer Science, Aberystwyth University, Aberystwyth, Ceredigion SY23 3DB, UK.
J Exp Biol. 2024 Mar 1;227(5). doi: 10.1242/jeb.246275. Epub 2024 Mar 12.
Pectoral fins play a crucial role in fish locomotion. Despite fishes living in complex fluid environments that exist in rivers and tidal flows, the role of the pectoral fins in navigating turbulent flows is not well understood. This study investigated the kinematics and muscle activity of pectoral fins in rainbow trout as they held station in the unsteady flows behind a D-section cylinder. We observed two distinct pectoral fin behaviors, one during braking and the other during Kármán gaiting. These behaviors were correlated to whole-body movements in response to the hydrodynamic conditions of specific regions in the cylinder wake. Sustained fin extensions during braking, where the fin was held out to maintain its position away from the body and against the flow, were associated with the cessation of forward body velocity, where the fish avoided the suction region directly downstream of the cylinder. Transient fin extensions and retractions during Kármán gaiting controlled body movements in the cross-stream direction. These two fin behaviors had different patterns of muscle activity. All braking events required recruitment from both the abductor and adductor musculature to actively extend a pectoral fin. In contrast, over 50% of fin extension movements during Kármán gaiting proceed in the absence of muscle activity. We reveal that in unsteady fluid environments, pectoral fin movements are the result of a complex combination of passive and active mechanisms that deviate substantially from canonical labriform locomotion, the implications of which await further work on the integration of sensory and motor systems.
胸鳍在鱼类游动中起着至关重要的作用。尽管鱼类生活在河流和潮汐流等复杂的流体环境中，但胸鳍在湍流导航中的作用尚未得到充分了解。本研究调查了虹鳟鱼在D型圆柱体后方的不稳定水流中保持静止时胸鳍的运动学和肌肉活动。我们观察到两种不同的胸鳍行为，一种在制动时，另一种在卡门步态时。这些行为与鱼体对圆柱体尾流中特定区域水动力条件的整体运动相关。制动时持续的鳍伸展，即鳍伸展以保持其远离身体并逆着水流的位置，与鱼体向前速度的停止相关，此时鱼避开了圆柱体正下游的吸力区域。卡门步态时短暂的鳍伸展和收缩控制了鱼体在横向的运动。这两种鳍行为具有不同的肌肉活动模式。所有制动事件都需要外展肌和内收肌募集来主动伸展胸鳍。相比之下，卡门步态期间超过50%的鳍伸展运动是在没有肌肉活动的情况下进行的。我们发现，在不稳定的流体环境中，胸鳍运动是被动和主动机制复杂组合的结果，这与典型的扇动式游动有很大不同，其影响有待于在感觉和运动系统整合方面开展进一步研究。
