Page 108 - Design in Nature

106 DESIGN IN NATURE

Water intake Opening

Fin
Expulsion pipe
Mantle wall
Inner organs
Gill

Enlarged position

Flexed position
Contracted position
Water intake

Water expulsion Pipe opening

Pipe

Shown in the figure are the jet propulsion cycle
and sections of the cuttlefish. The cycle begins
with enlargement (1). The outside diameter of the
body is enlarged by 10% of the normal size,
which increases the volume of the mantle cavity
by about 22%. Water enters from the openings on
both sides of the head passing through the funnel-shaped pipe. When the maximum
enlargement is reached, the diameter of the body is reduced to 75% of normal size (2).
Pressure in the cavity suddenly increases and pushes the inner tap on the mouth of
flushing-out pipe, which closes the water intake. Nearly all the water (approximately 60% of
normal body size) is forcefully expelled out through the pipe. The body recovers its normal
shape by the intake of water (3). Any further contractions could easily harm the creature.
The jet propulsion lasts about one second and can be repeated 6 to 10 times in a row,
including suction time. When swimming slowly the body of the cuttlefish contracts to 90%
of its original size.