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. 2015 Oct 20:6:8638.
doi: 10.1038/ncomms9638.

Electric eels use high-voltage to track fast-moving prey

Kenneth C Catania  1
Affiliations

Electric eels use high-voltage to track fast-moving prey

Kenneth C Catania. Nat Commun. .

Abstract

Electric eels (Electrophorus electricus) are legendary for their ability to incapacitate fish, humans, and horses with hundreds of volts of electricity. The function of this output as a weapon has been obvious for centuries but its potential role for electroreception has been overlooked. Here it is shown that electric eels use high-voltage simultaneously as a weapon and for precise and rapid electrolocation of fast-moving prey and conductors. Their speed, accuracy, and high-frequency pulse rate are reminiscent of bats using a 'terminal feeding buzz' to track insects. Eel's exhibit 'sensory conflict' when mechanosensory and electrosensory cues are separated, striking first toward mechanosensory cues and later toward conductors. Strikes initiated in the absence of conductors are aborted. In addition to providing new insights into the evolution of strongly electric fish and showing electric eels to be far more sophisticated than previously described, these findings reveal a trait with markedly dichotomous functions.

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Figures

Figure 1
Figure 1. Electric eel senses and discharge.
(a) Eel colourized to show electroreceptors (magenta) and mechanoreceptors-neuromast canals (blue). (b) The weak, low-voltage output used for electrolocation and the high-voltage, high-frequency output used as a weapon. (c) Schematic illustration of electrolocation based on the convergence of electric field lines on the eel's skin (arrow).
Figure 2
Figure 2. Paradigm showing that electric eels find and attack conductors.
(a) Recording and stimulator configuration that triggered pithed-fish twitch and eel attack in the presence of six plastic rods and one conductor (arrow). (b) Plates from high-speed movie (top) and real-time (bottom) of same trial illustrating circuitous path to conductor. (c) Eel low- and high-voltage discharge marked with short, and tall ticks, respectively, illustrating the exclusive use of high-voltage during strike movement. (d) Eel path to conductor.
Figure 3
Figure 3. Eel conductor tracking under 940 nm IR illumination.
(a) Schematic of paradigm and eel tracking behaviour and suction-feeding strike to conductor. (b) Eel low and high voltage discharge marked with short, and tall ticks, respectively, illustrating the exclusive use of high-voltage during strike movement. (c) Eel track relative to conductor movement. Inset shows hole in agar (arrow) that was directly over conductor at suction onset.
Figure 4
Figure 4. Schematic of paradigm used to illustrate tracking strike under full spectrum illumination along with plates from real-time video.
A single conductor was inserted along with 15 plastic non-conductors of similar appearance. For clarity, added red arrow marks the conductor in figure, which was indicated on the disk with a smaller arrow. The eel rapidly accelerated to catch up to the conductive stimulus, then tracked the stimulus as is initiated a suction-feeding strike. For reference, each disk is 2.54 cm wide, centered on a circle of 16.5 cm diameter, spinning at a rate of 0.88 revolutions per second (see Supplementary Movie 6).
Figure 5
Figure 5. Eel tracking fish below agar barrier under 940-nm infrared illumination.
(a) Plates from movie with dual, 940-nm diodes indicating high-voltage output. (b) Eel track with plates marked (circles). (c) Eel low- and high-voltage discharge marked with short, and tall ticks, respectively, illustrating the exclusive use of high-voltage during strike movement. Circles mark timing of plates in a. Scale bar, 4 cm.
See this image and copyright information in PMC

References

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