Swimming in the upside down catfish Synodontis nigriventris:: it matters which way is up
Swimming in the upside down catfish Synodontis nigriventris:: it matters which way is up
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DOI：
10.1242/jeb.006437
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发表时间：
2007-09-01
影响因子：
2.8
通讯作者：
Chan, Keith H. S.
中科院分区：
文献类型：
--
作者：
Blake, Robert W.;Chan, Keith H. S.
黑腹歧须鲨是一种兼性的水面呼吸动物，其动物学上的腹面朝向水面，游泳时会倒过来。它们的近水面阻力大约是深潜阻力（由于波浪阻力）的两倍，大约是摩擦阻力和压力阻力之和的两倍。对于流线型技术体，近水面的波阻增加值可能是深潜值的五倍。然而，对于鱼和流线型技术机构，阻力的深度依赖性是相似的，在表面以下约3个身体直径处增加消失。阻力'倒置'大约是15%小于'背侧向上'表面附近。与此相一致，在任何给定的速度，尾拍频率较低，步幅较大的倒置游泳在表面接近（P <0.05）。在深潜状态下，不同体位的阻力和运动学差异无显著性（P> 0.05）。在临界弗劳德数为0.45时，接近水面的速度对应于以疲劳结束的长时间游泳。为了超过这些速度，鱼必须在深水中游泳，这种行为被观察到。反向游泳有助于有效的空气呼吸。在水面呼吸过程中，背侧向上的阻力是倒置姿势值的1.5倍。快速启动是直线的，直接远离刺激。平均和最大速度和加速度在表面接近度上降低（P <0.05），并且更高的倒置（最大加速度：20 - 30 m s（-2）; P <0.05），并且与运动通才相当（e. G.鳟鱼）。由于波浪产生的机械能损失约为20%的倒置和40%的背侧向上，低于鳟鱼在浅水中快速启动（70%的损失）;底部效应和大振幅C启动（c。F. S. nigriventris）增强鳟鱼的抗性。S. nigriventris可能是从一个昼夜或黄昏'Chiloglanis样'底栖祖先进化而来。夜间性和反向反遮蔽可能与倒置习惯共同进化。据推测，水面游泳增加的能量成本通过利用空气-水界面用于食物和/或空气呼吸来抵消。
Synodontis nigriventris is a surface- feeding facultative air-breather that swims inverted with its zoological ventral side towards the water surface. Their near-surface drag is about double the deeply submerged drag ( due to wave drag) and roughly twice the sum of frictional and pressure drags. For streamlined technical bodies, values of wave drag augmentation near the surface may be five times the deeply submerged values. However, the depth dependence of drag is similar for fish and streamlined technical bodies, with augmentation vanishing at about 3 body diameters below the surface. Drag 'inverted' is approximately 15% less than that 'dorsal side up' near the surface. Consistent with this, at any given velocity, tailbeat frequency is lower and stride length higher for inverted swimming in surface proximity ( P< 0.05). Deeply submerged, there are no significant differences in drag and kinematics between postures ( P> 0.05). At the critical Froude number of 0.45, speeds in surface proximity correspond to prolonged swimming that ends in fatigue. To exceed these speeds, the fish must swim deeply submerged and this behaviour is observed. Inverted swimming facilitates efficient air breathing. Drag dorsal side up during aquatic surface respiration is 1.5 times the value for the inverted posture. Fast-starts are rectilinear, directly away from the stimulus. Average and maximum velocity and acceleration decrease in surface proximity ( P< 0.05) and are higher inverted ( maximum acceleration: 20 - 30 m s(-2); P< 0.05) and comparable to locomotor generalists ( e. g. trout). Mechanical energy losses due to wave generation are about 20% for inverted and 40% for dorsal side up, and lower than for trout fast-starting in shallow water ( 70% losses); bottom effects and large amplitude C-starts ( c. f. relatively low amplitude rectilinear motions in S. nigriventris) enhance resistance in trout. S. nigriventris probably evolved from a diurnal or crepuscular 'Chiloglanis-like' benthic ancestor. Nocturnality and reverse countershading likely co-evolved with the inverted habit. Presumably, the increased energy cost of surface swimming is offset by exploiting the air - water interface for food and/or air breathing.