Like all electric fish, electric eels use
the production and sensing of weak electrical signals for navigation
and for social communication with other electric eels in dark
or murky waters. The fish have small eyes and poor
eyesight, which worsens as the fish ages. The electrical
sensors are a modification of the lateral line, a row of pits
that fish usually use as pressure sensors. The lateral
line can be seen in the picture above just at the margin of
the more darkly pigmented dorsal side of the fish. The
fishes' reading of their electrical environment is something
like echolocation in bats or in dolphins. Some of the
electrical receptors are tuned to the transmissions of non-electrical
fish; others are specialized for detecting the signals of the
fish itself. Their ability to detect electrical signals
even allows them to detect the heartbeat of other fish.
They get the best "picture" of their surroundings if the body
is held relatively rigid. The rippling anal fin allows
the animal to propel itself through the water with little side-to-side
bending of the body. The presence of pollutants in the
water can alter the signal emitted by the fish, and a study
in France is testing the possibility of using the fish to
monitor water quality.
The electric eel is different from other
electric fish in its ability to generate a stunning or even
a killing electrical discharge. The electric eel can produce
up to 600V in a single dischange -- this is 5 times the shock
you would get from sticking your finger into an electrical socket.
David Attenborough, in his TV series Life
On Earth, demonstrated how the electrical current produced
by an electric eel could be used to turn one of more light bulbs!
The electric organ, which consists of a series of modified tail
muscles, is similar to a row of batteries connected in a series.
It is subdivided into three sections: two small and one
large. One small battery is used for navigational signals.
The large battery and the other small one is used to generate
the stunning discharge. After delivering a strong shock,
the electric eel must then allow the electric organ to recharge.
Batteries have to be recharged using an external source of energy;
in the electric eel the energy to recharge the electric organ
comes from the fish's metabolism.
A discharge from an electric eel can kill
the small fish that are its primary food, but electric eels
can also shock potential predators. A touch from the electric
eel's tail can effectively disable a human or a large animal
with a stunning shock, although a single discharge is usually
not enough to kill. However repeated shocks could
kill, and falling over in the water after a disabling discharge
could result in drowning. An electric eel would NOT make
a good pet!
Electric eels are air-breathing fish that
use vascular folds in the lining of the mouth for absorbing
oxygen. Air is taken in through the mouth and out through
the gill slits. If you watch the fish in the Record Aquarium
for a few minutes, you will see it rise to the surface to breath.
Nearly 80% of the oxygen used by the fish is taken in this way.
