Hunting archer fish match their take-off speed to distance from the future point of catch
Hunting archer fish match their take-off speed to distance from the future point of catch
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DOI：
10.1242/jeb.01981
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发表时间：
2006-01-01
影响因子：
2.8
通讯作者：
Schuster, S
中科院分区：
文献类型：
--
作者：
Wöhl, S;Schuster, S
射箭鱼可以用锋利的水流射落昆虫猎物。鱼通常从不直接位于目标下方的位置射击，因此被驱逐的昆虫会以水平速度分量弹道坠落。昆虫走上路径后仅 100 毫秒，射击者和其他虫群成员就可以快速转弯，然后径直朝失败的猎物的下一个撞击点方向前进。根据坠落昆虫运动的初始值，快速转弯和随后的起飞是“开环”执行的。我们在这里报告，射箭鱼不仅可以向后来撞击点的方向起飞，还可以预测其距离。距离信息使鱼能够调整它们的起飞速度，以便它们能够在猎物撞击后在一个狭窄的时间段内（大约 50 毫秒）到达，尽管对齐转弯的大小和要覆盖的距离存在很大差异。选择具有匹配速度的恒速程序并捕捉移动中的昆虫可以最大限度地减少摩擦损失。起鱼的初始速度稍微但系统性太慢，随后会增加，使得鱼比预期提前 20 毫秒到达，并且通常会以高于起飞速度的速度进行捕获。后来速度变化的可变性表明起飞时存在系统性“错误”，就好像鱼低估了距离一样。然而，这种明显的缺陷似乎很好地适应了鱼高速捕捉猎物的情况：如果后来鱼无法纠正最初的错误，那么最好开始稍微慢一点，以尽量减少超过捕捉点的风险。
Archer fish can shoot down insect prey with a sharp jet of water. Fish usually fire from positions that are not directly below their target so that a dislodged insect falls ballistically with a horizontal velocity component. Only 100 ms after the insect is on its path both the shooter and other school members can initiate a rapid turn and then head straight in the direction of the later point of impact of their failing prey. The quick turn and subsequent takeoff are performed 'open-loop', based on the initial values of the falling insect's motion. We report here that archer fish can not only take off in the direction of the later point of impact but also predict its distance. Distance information allows the fish to adjust their take-off speed so that they would arrive within a narrow time slot slightly (about 50 ms) after their prey's impact, despite large differences in the size of the aligning turn and in the distance to be covered. Selecting a constant speed program with matched speed and catching the insect on the move minimizes frictional losses. The initial speed of starting fish is slightly but systematically too slow and is increased later so that the fish arrive 20 ms earlier than expected and often make the catch on a higher than take-off speed. The variability of later speed changes suggests a systematic 'error' in the take-off, as if the fish underestimated distance. However, this apparent deficiency seems well adapted to the fish catching their prey at a high speed: if later the fish had no possibility to correct an initial error then it is better to start slightly too slow in order to minimize the risk of overshooting the point of catch.