Department of Evolution & Ecology, University of California, One Shields Ave., Davis, CA 95616, USA.
Zoology (Jena). 2010 Mar;113(2):75-84. doi: 10.1016/j.zool.2009.08.002. Epub 2010 Feb 25.
We examined the effects of variation in swimming speed, or 'ram speed', on the feeding kinematics of juvenile Indo-Pacific tarpon, Megalops cyprinoides. Tarpon were filmed feeding on non-elusive prey at 500 images s(-1). Prey items were offered at one end of the filming tank, the opposite end where tarpon grouped, to encourage them to use a ram strategy to capture their prey. We describe tarpon as ram-suction feeders. Ram speed varied among strikes from 0.19 to 1.38 m/s and each individual produced speeds that spanned at least 0.9 m/s across trials. Although suction distances were much less variable, prey movement towards the predator was present in all feeding trials. There was a strong positive relationship between initial predator - prey distance and ram speed (r(2)=0.72, P<0.001). When tarpon initiated their strike from further away, they achieved higher ram speeds, but also took longer to capture their prey. All other timing variables were unaffected by ram speed whereas at higher ram speeds tarpon exhibited greater expansion of the mouth and buccal cavity. Greater buccal expansion accomplished in the same period of time implies that both the total volume of water captured and the water flow rate entering the mouth was greater in strikes at higher ram speeds. Our results demonstrate how feeding kinematics may vary as a function of ram speed, and how fish predators that lack jaw protrusion and have a large gape capacity can maximize their feeding success by altering their swimming speed.
我们研究了游泳速度（或“水击速度”）变化对幼年亚洲海鲢（Megalops cyprinoides）摄食运动学的影响。使用 500 帧/秒的速度拍摄亚洲海鲢捕食非逃避性猎物的视频。在拍摄水箱的一端投喂猎物，在另一端亚洲海鲢聚集，以鼓励它们使用水击策略来捕获猎物。我们将亚洲海鲢描述为水击抽吸式摄食者。水击速度在各个咬击之间变化范围为 0.19 至 1.38 米/秒，每个个体在试验中产生的速度至少跨越 0.9 米/秒。尽管抽吸距离的变化小得多，但在所有摄食试验中都存在猎物向捕食者移动的情况。初始捕食者-猎物距离与水击速度之间存在很强的正相关关系（r²=0.72，P<0.001）。当亚洲海鲢从更远的地方开始攻击时，它们会达到更高的水击速度，但也需要更长的时间来捕获猎物。所有其他时间变量都不受水击速度的影响，而在更高的水击速度下，亚洲海鲢的口部和口腔扩张更大。在相同的时间内实现更大的口腔扩张意味着在更高的水击速度下，捕获的水总体积和进入口腔的水流速度都更大。我们的研究结果表明，摄食运动学如何随着水击速度的变化而变化，以及缺乏下颚突出和具有大张合度的鱼类捕食者如何通过改变游泳速度来最大限度地提高其摄食成功率。
