Higham Timothy E, Day Steven W, Wainwright Peter C
Section of Evolution and Ecology, University of California, One Shields Avenue, Davis, CA 95616, USA.
J Exp Biol. 2006 Jul;209(Pt 14):2713-25. doi: 10.1242/jeb.02315.
Suction feeding fish draw prey into the mouth using a flow field that they generate external to the head. In this paper we present a multidimensional perspective on suction feeding performance that we illustrate in a comparative analysis of suction feeding ability in two members of Centrarchidae, the largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus). We present the first direct measurements of maximum fluid speed capacity, and we use this to calculate local fluid acceleration and volumetric flow rate. We also calculated the ingested volume and a novel metric of strike accuracy. In addition, we quantified for each species the effects of gape magnitude, time to peak gape, and swimming speed on features of the ingested volume of water. Digital particle image velocimetry (DPIV) and high-speed video were used to measure the flow in front of the mouths of three fish from each species in conjunction with a vertical laser sheet positioned on the mid-sagittal plane of the fish. From this we quantified the maximum fluid speed (in the earthbound and fish's frame of reference), acceleration and ingested volume. Our method for determining strike accuracy involved quantifying the location of the prey relative to the center of the parcel of ingested water. Bluegill sunfish generated higher fluid speeds in the earthbound frame of reference, accelerated the fluid faster, and were more accurate than largemouth bass. However, largemouth bass ingested a larger volume of water and generated a higher volumetric flow rate than bluegill sunfish. In addition, because largemouth bass swam faster during prey capture, they generated higher fluid speeds in the fish's frame of reference. Thus, while bluegill can exert higher drag forces on stationary prey items, largemouth bass more quickly close the distance between themselves and prey. The ingested volume and volumetric flow rate significantly increased as gape increased for both species, while time to peak gape had little effect on the volume. However, peak gape distance did not affect the maximum fluid speed entering the mouth for either species. We suggest that species that generate high fluid speeds in the earthbound frame of reference will commonly exhibit small mouths and a high capacity to deliver force to buccal expansion, while species that ingest a large volume of water and generate high volumetric flow rates will have larger buccal cavities and cranial expansion linkage systems that favor displacement over force delivery.
吸食性鱼类利用它们在头部外部产生的流场将猎物吸入口中。在本文中，我们呈现了一个关于吸食性能的多维度视角，并在太阳鱼科的两个成员——大口黑鲈（Micropterus salmoides）和蓝鳃太阳鱼（Lepomis macrochirus）的吸食能力比较分析中进行了阐述。我们首次直接测量了最大流体速度，并以此计算局部流体加速度和体积流量。我们还计算了摄取量和一个新的攻击精度指标。此外，我们针对每个物种量化了口裂大小、口裂达到峰值的时间以及游泳速度对摄取水量特征的影响。利用数字粒子图像测速技术（DPIV）和高速视频，结合位于鱼体中矢面的垂直激光片，测量了每个物种三条鱼嘴前的水流。由此我们量化了最大流体速度（在地面参考系和鱼的参考系中）、加速度和摄取量。我们确定攻击精度的方法包括量化猎物相对于摄取水团中心的位置。在地面参考系中，蓝鳃太阳鱼产生的流体速度更高，使流体加速更快，并且比大口黑鲈更精确。然而，大口黑鲈摄取的水量更大，产生的体积流量比蓝鳃太阳鱼更高。此外，由于大口黑鲈在捕获猎物时游得更快，它们在鱼的参考系中产生的流体速度更高。因此，虽然蓝鳃太阳鱼对静止猎物施加的阻力更大，但大口黑鲈能更快地缩短自身与猎物之间的距离。对于两个物种而言，摄取量和体积流量都随着口裂的增大而显著增加，而口裂达到峰值的时间对摄取量影响不大。然而，口裂峰值距离对任一物种进入口中的最大流体速度都没有影响。我们认为，在地面参考系中产生高流体速度的物种通常会有小嘴以及向口腔扩张施加力的高能力，而摄取大量水并产生高体积流量的物种将有更大的口腔和颅骨扩张连接系统，这些系统更有利于位移而非力的传递。
