The secret of reasonable behavior jellyfish


01/05/2011

A closer look at the sky a set of eyes, belonging to box jellyfish provides evidence that these creations, which do not have a standard brain, able to behave intelligently. A new study shows that one type of jellyfish uses a set of eyes to swim under water and stay close to home.

"It’s amazing what a jellyfish as a pet, devoid of the brain and, therefore, the development of behavior can move under water due to the visual abilities, which is unusual behavioral task," - said the chief researcher Anders Garm (Anders Garm) from the University of Copenhagen. "This indicates that the ability of behavioral protozoa like jellyfish may be underestimated." In the box jellyfish have 24 eyes of four different types, and two of them - the upper and lower lens eyes - can form images and resemble the eyes of vertebrates like humans. Other eyes are more primitive. It is already known that the vision of jellyfish-box allows them to perform simple tasks, such as respond to light and avoid obstacles.

In the new analysis, the researchers found that a type of box jellyfish-cubic (Tripedalia cystophora), uses its upper lens eyes, which are located in four cup-like structures to make sure that the animal is close to the roots of mangrove trees that define their environment habitat.

This species lives on the surface of the Caribbean mangrove swamps where they feed on small crustaceans that live in the roots of mangrove trees. If jellyfish drift away too far from these places, it runs the risk of dying from hunger, according to the information of the researcher.

The researchers took pictures underwater, looking up to mimic the look of jellyfish when it is removed from the mangroves. Using these images, as well as the model of an eye, they were able to simulate the image formed in the retina at the back of her hand side to find that even at a distance of 10 meters jellyfish can see the roots of the mangrove canopy.

They then they spent a behavioral test using wild-box jellyfish in Puerto Rico. When the jellyfish has been moved to 5 meters from its habitat, it quickly swam back to the nearest tree. And when the animal was placed in a plastic jar under a canopy of tree roots, jellyfish swam randomly. But as soon as the bank moved a certain distance from the roots of mangrove jellyfish started trying to get back to them, the behavior of which was strong when the animal was at a distance of 2-4 meters from the lagoon. When the jellyfish has been moved to 12 meters from its habitat, she floated randomly. And if the kind of tree roots for it was unclear jellyfish lost its direction.

Eyes are used only for visual purpose may be an early stage in the evolution of the visual systems of animals, and this system is used, the box jellyfish may require fewer manufacturing processes than the system wherein the pair of eyes only performs many functions, such as it occurs in humans.

"The actions of the box jellyfish can thus be linked to the lack of a central brain, but this is contrary to the view that the central brain is a prerequisite for the development of behavior" - the researchers reported April 28 in the journal "Current Biology".

Original: LiveScience Translation: M. Potter


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