|
Mantis shrimps (Stomatopods) are known for the feeding
tubes they use to break the shells of their prey and the way they kick
as fast as bullets. According to a recent study published in Nature
magazine, the kicks of the mantis shrimp belonging to the species Odontodactylus
scyllarus are grounded in a special spring mechanism. (click
for images)
 Mantis
shrimp are predatory crustaceans that live in shallow regions of tropical
and subtropical seas. These shellfish range between 2 and 70 cm in length
and are some of the most aggressive of all living things. They take their
scientific names from the manner in which they feed and the appendages
that extend from their chests (stomato: mouth; pod: foot). Each of these
is clawed, the second being particularly large and used in striking and
seizing prey. These creatures are widely known as "mantis shrimp"
because the bristly appearance of the second appendage resembles that
of the preying mantis. These appendages come in two types, speared and
heeled, and vary among species. Gills emerge from the appendages that
extend out of the stomach, and these may be used in swimming. Mantis shrimp
use their second appendages in breaking the shells of snails, their principle
source of food. These kicks are very powerful. A large mantis shrimp can
strike with the force of a 22-caliber bullet. (1)
Previous researchers reported that mantis shrimp struck at a maximum
speed of 10 metres per second. However, in this latest study of a faster
mantis shrimp, carried out using new imaging technology, it was revealed
that the creatures are able to punch out their appendages at between 14
and 23 metres per second. This research, performed by scientists from
the California University Integrative Biology Department (2),
demonstrated that this speed is produced thanks to a specialized spring
system.
The elastic tension energy produced by the muscle fibres and tendon is
insufficient by itself to extend the appendage at that speed. According
to the scientists' calculations, a blow at this speed requires a force
of 4.7 x 105 watts per kilogram of muscle. Yet it is impossible, according
to our present knowledge, for such a force to be produced by even the
quickest contracting muscles. That is why the scientists account for the
mantis shrimp kick in terms of the presence of a specialized spring system.
Since mantis shrimp generate these movements in a dense water environment
they quickly expend large amounts of energy, for which reason they employ
a specialized spring system. This mechanism works like a catapult: the
moment the muscles attached to the appendage start to contract the flexor
muscles, another group of muscles that serve as a catch, go into action
by delaying the movement of the appendage. When the muscles attached to
the appendage achieve maximum contraction the catches are released. The
appendage is thus thrown out very fast. A mantis shrimp strike takes place
in as little as two milliseconds (2/1000 of a second), fifty times faster
than the human eye can see. (3) (Click
here for diagram of strike mechanism)
According to the scientists' report, the seat of this spring mechanism
has a hyperbolic-parabolic form used in engineering and architecture.
In structures built in this shape, opposing and diagonal arcs reduce tensions
by distributing them along the three-dimensional surface. The risk of
collapse is thus reduced. In a similar way, the fact that the seat of
the mantis shrimp spring mechanism is saddle shaped prevents collapse
by reducing the effect of the forces arising during compressing and extending.
It is quite astonishing that the mantis shrimp should use a design principle
employed by engineers and architects. Unlike intelligent architects and
engineers, it is impossible for a mantis shrimp to know the mathematical
bases of this principle and make designs accordingly.
A mantis shrimp that sees the hardness of the shell of the snail it has
selected as its prey cannot think of and realise the production of a weapon
to overcome this in its own body. It is impossible for it first to produce
spears or heels in its front appendages, then to plan a spring system
to fire these, and then to develop the muscles attached to the appendage
and the flexor muscles that delay the firing thereof. It is clear, therefore,
that the mantis shrimp was created together with this system. There is
no doubt that Almighty God, the Lord of the Worlds, brought the mantis
shrimp into being. God is He Who creates with no previous model. In one
verse from the Qur'an our Lord states:
[God is] the Originator of the heavens and Earth. When
He decides on something, He just says to it, "Be!" and it is.
(Qur'an, 2: 117)
Note: If you wish to see how a mantis shrimp breaks a snail shell click
here.
(Quick Time is required)
1 "Seeing the World in Many Colors", Maryland
University Internet Site, http://www.umbc.edu/gradschool/research/profile_11.html
2 S. N. Patek, W. L. Korff & R. L. Caldwell, "Biomechanics: Deadly
strike mechanism of a mantis shrimp," Nature 428, 22 April 2004,
pp. 819 - 820
3 "Secrets of the Stomatopod: An Underwater Research Adventure",
California University Internet Site, http://www.ucmp.berkeley.edu/aquarius/raps.html
|
