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(Marcin) #1

66 Scientific American, April 2019










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The closer the positive
and the negative, the
stronger the field

Voltage
experienced
by prey

High-voltage
doublet

Involuntary
prey movement

High-voltage
attack volley

Low-voltage
electroreception

Eel’s Voltage Output^500
volts

1 2 3 4

Attack Mode


Like a Taser, an electric eel on the hunt emits pulses of electricity to in ­
capacitate prey. The eel’s zaps activate the motor neurons that control
the prey’s muscles. In this way, the eel can be said to have remote control
over prey. It uses this remote control in two ways: to reveal hidden prey
by making them twitch and then to freeze the prey once they have been

located, preventing escape. The eel can also use its electricity to
track moving prey. And it has evolved an ingenious solution to
a fundamental challenge of operating in the aquatic realm,
where much of the electricity in its stunning strikes
would typically be lost to the surrounding water.

Focused Intensity
Eel’s electric field is what physicists term
a dipole: lines representing forces on a positive
charge originate from the positive head of the
eel and end on the negative tail. The density
of lines indicates the strength of the electric
field at any given point. Bringing the positive
pole closer to the negative pole increases the
field strength between them. The eel does
this by curling its tail around the prey
gripped in its mouth before zapping it.

SOURCES: “ELECTRIC EELS CONCENTRATE
THEIR ELECTRIC FIELD TO INDUCE INVOLUNTARY
FATIGUE IN STRUGGLING PREY,” BY KENNETH C. CATANIA,
IN CURRENT BIOLOGY, VOL. 25, NO. 22; NOVEMBER 16, 2015, AND
“THE SHOCKING PREDATORY STRIKE OF THE ELECTRIC EEL,”
BY KENNETH CATANIA, IN SCIENCE, VOL. 346; DECEMBER 5, 2014

Illustrations by Matthew Twombly
Free download pdf