Live spiders hang upside down to save energy

A group of scientists from various fields from Spain and Croatia conducted an investigation of the eccentric life of many spiders living, eating, reproducing and 'walking' in an upside-down posture. According to their findings, an unusual mechanism formed the shape of spiders to provide high energy efficiency, similar to vibrating pendulum.

Most terrestrial animals evolved to use the ground as their main support for their movement. Therefore, their legs evolved to be able to support the weight of the whole body, allowing them to move with the head higher than the leg. However, many spiders feel that the reverse world seems more convenient. They spend most of their lives hanging upside down on their feet, and 'going' by swinging under the action of gravity.

Excited by this evolutionary phenomenon, a group of biologists from the CSIC, Almería, Spain center, together with astrophysicist at Split University, Croatia, conducted an investigation of the advantages of Biology and signs of an unusual lifestyle by studying over a hundred species of spiders. One of their key questions is the evolutionary importance of 'north silk' - the ability of many spiders to travel between plants far apart by spreading bridges with spider silk and ice. through them when in position to hang upside down on the ground,

A 'backwards' spider, Uloborus, Almería (Spain) (Photo: Eva De Mas)

Previous work by other authors has shown that for monkeys hanging position can save energy more than the usual way of moving on the ground. Following this finding, scientists experimented with many spiders and compared two different ways of moving - walking on the ground and north from one branch to another.

Dr Jordi Moya-Laraño, Spain, the principal researcher of the project, said: 'We found that live spiders hanging upside down have evolved their legs longer than regular spiders, allowing them to move. through spider silk faster than normal walking on the ground. In particular, these spiders move 'clumsy' bigger, because their long legs - convenient for twisting - do not allow them to easily lift the heavy body. '

For Dr. Dejan Vinkovi, an astrophysicist from Croatia, this study is not only biologically significant.'As a physicist, I am particularly interested in the energy of the reverse hanging position. By this work we finally proved that the energy efficiency of this type of motion originates from a physical principle used to run ancient clocks - the movement of the pendulum under the influence of gravity. '

Dr. Eulalia Moreno, co-author of the work, added: 'We started working with Dr. Moya-Laraño because I studied the shape and function of the corn fin bird, the same bird as the spider, hanging upside down while eating. Now, we understand better how the animal's shape will evolve if they spend most of their time hanging upside down. '

These results have implications for the evolution and ecosystem of spiders. For example, small spiders hanging on spider webs can crawl on the ground to hunt, like in some tiny spiders, which large spiders cannot do better.