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Home page > Animal Kingdom > The system that protects the bones of hibernating bears discovered

The Mantis Shrimp's Deadly Kicking Mechanism
Animal Kingdom


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.

Its eyes gives it an almost 360-degree feeld of vision and a three dimensional image. The red appendagesaround the green scales are related to the sense of smell and scan scent molecules in the water.

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)

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 peacock mantis shrimp takes a whack at a Tegula snail with its front leg, which can reach speeds of 75 feet per second. (Sheila Patek, Wyatt Korff/UC Berkeley)

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.

References:
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

 
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