Science_Illustrated_Australia_-_Issue70_2019

Cartilage

Fish uses electricity to hunt

By emitting ripples of electrical signals from tail muscles, this

elephant-nose fish can hunt in pitch darkness. Sensitive cells in its

‘chin’ and elsewhere function as receptors to pick up the echo of prey.

Waves of electricity scan

the dark river water

The elephant-nose fish emits electrical signals

from two muscle bundles in its tail-head.

This happens up to 100 times per second. The electric

signals spread like rings in the water around the

elephant-nose fish. Special skin receptors sense

reflections of these signals, which are interrupted

by objects in the water, such as prey. The skin

receptors register the interruptions and send a

message to the brain. Based on the messages

from the many receptors, the brain produces an

internal 3D image of the unknown object.

The chin is hyper-sensitive

The skin on the trunk-like mouth extension

of Gnathonemus petersii, also known as

Peters’ elephant-nose fish, is equipped with 500

of its skin’s total 4000 receptors. So this ‘chin’ is

extra sensitive to weak electric signals from prey

hidden in the mud of a river bed, which are ‘illumi-

nated’ by signals emitted from its tail. The skin is

highly insulating so it does not allow passage of

electrical impulses direct from the tail muscles.

The receptors consist of two slime-filled insulating

chambers that control separate receptor cells.

Receptor

cell

Inner

chamber

Muscle

Skin surface

Electric

organ

Electricalsignal

Nerve path

chamOuter ber

Connective tissue

Diffuse reflection

Clear reflection

farBall^

away

cloBsall^

e by

CLOSE

FAR AWAY

ELEPHANT-NOS

USES P E^ FISH^

OWER AS A RUL

(^) Biologis ER
ts have studied the
elephant-nose fish
’s ability to measure
distances by placing balls i
positions. The n^ different
scientists (^) discovered
that the fish can (^) estim
down to a ate^ distances
few millimetres by
electrical sense. T using its
he fish (^) uses (^) the fact
that (^) the electric reflection
ball becomes^ from^ the
ever more vague w
distance. Based (^) on th ith
the fish e^ degree^ of^ clarity,
estimates (^) the distan
ce.
100 signa
ls^ per
second^ em
itted.^
CLAUS LUNAU & PAT MORRIS/ARDEA.COM
Cross-section of
electroreceptor