Living upside-down shapes spiders for energy savingMarch 26, 2008An interdisciplinary team of researchers from Spain and Croatia led an investigation into the peculiar lifestyle of numerous spider species, which live, feed, breed and 'walk' in an upside-down hanging position. According to their results, such 'unconventional' enterprise drives a shape in spiders that confers high energy efficiency, as in oscillatory pendulums. These results will appear in this week's issue of PLoS ONE. The great majority of land animals evolved to use the ground as the main support for their motion. Accordingly, they evolved legs capable of supporting the weight of their whole bodies, enabling them to move around with their heads above their feet. However, many spider species found it more convenient to literally turn their world upside down. They spend most of their lives hanging suspended by their legs, and 'walk' by swinging under the influence of gravity. Intrigued by this evolutionary phenomenon, a team of biologists from the Estación Experimental de Zonas Áridas (CSIC, Almería) in Spain, joined by an astrophysicist from the University of Split, Croatia, conducted an inquiry into biological advantages and caveats of such a peculiar lifestyle by studying over a hundred spider species. One of their focal questions was the evolutionary importance of 'bridging' - the technique many spiders use to move between remote plants by building their own silk bridges, which they cross by 'walking' suspended upside-down from them. Earlier research by other authors indicated that for monkeys this suspensory way of locomotion might be a more energetically efficient way of transportation than 'regular' walking on the ground. To this end, the authors took several spider species into the laboratory and compared how they handle two different types of movement - walking on the ground and bridging from branch to branch. "We discovered that spiders that live upside-down have evolved disproportionately longer legs relative to 'normal' spiders, which enables them to move faster while bridging than while 'normally walking' on the ground. Particularly 'clumsy' walkers are larger spiders, because their long legs - otherwise so convenient for bridging - do not allow an easy lifting of their relatively large body mass" says Dr. Jordi Moya-Laraño from Spain, the principal investigator on this project. For Dr. Dejan Vinković, astrophysicist from Croatia, this research is more than a biology study. "As a physicist, I was particularly interested in the energetics of upside-down locomotion" he says. "With this research we finally proved that the energetic efficiency of such motion stems from the same physical principle used to run the grandfather's clock - motion of a pendulum under the influence of gravity." Dr. Eulalia Moreno, co-author of the study, adds: "We started this collaboration with Dr. Moya-Laraño because I had studied the form and function of legs in tits, birds that, similarly to spiders, hang upside-down while foraging. Now, we have a much better understanding of how an animal shape should evolve when animals spent most of their lifetime hanging upside-down" These results have implications for the evolution and ecology of spiders. For example, small spiders that hang from their webs should be able to leave their webs in search for prey by walking on the ground, as found in some tiny spiders, something that large spiders will be unable to do efficiently. Public Library of Science |
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| Related Spiders Current Events and Spiders News Articles Shedding light on the cosmic skeleton "Matter is not distributed uniformly in the Universe," says Masayuki Tanaka from ESO, who led the new study. "In our cosmic vicinity, stars form in galaxies and galaxies usually form groups and clusters of galaxies. The most widely accepted cosmological theories predict that matter also clumps on a larger scale in the so-called 'cosmic web', in which galaxies, embedded in filaments stretching between voids, create a gigantic wispy structure." Spider web glue spins society toward new biobased adhesives With would-be goblins and ghosts set to drape those huge fake spider webs over doorways and trees for Halloween, scientists in Wyoming are reporting on a long-standing mystery about real spider webs: It is the secret of spider web glue. Scientists discover largest orb-weaving spider Researchers from the United States and Slovenia have discovered a new, giant Nephila species (golden orb weaver spider) from Africa and Madagascar and have published their findings in the Oct. 21 issue of the journal PLoS ONE. First 'mainly vegetarian' spider described The 40,000 or so spiders that have been described are generally known as strict predators, trapping their prey in elaborate webs or hunting them down directly. Herbivory discovered in a spider There are approximately 40,000 species of spiders in the world, all of which have been thought to be strict predators that feed on insects or other animals. Now, scientists have found that a small Central American jumping spider has a uniquely different diet: the species Bagheera kiplingi feeds predominantly on plant food. Researchers go underground to reveal 850 new species Australian researchers have discovered a huge number of new species of invertebrate animals living in underground water, caves and "micro-caverns" amid the harsh conditions of the Australian outback. U of T scientists identify gene that has enabled water striders to glide across water Water striders, the familiar semi-aquatic bugs gliding across the lake at the cottage, have a novel body form that allows them to walk on water. Researchers to study rebirth of an island after volcanic eruption When Alaska's Kasatochi Volcano erupted on Aug. 7, 2008, it virtually sterilized Kasatochi Island, covering the small Aleutian island with a layer of ash and other volcanic material several meters thick. Scary ancient spiders revealed in 3-D models, thanks to new imaging technique Early relatives of spiders that lived around 300 million years ago are revealed in new three-dimensional models, in research published today in the journal Biology Letters. Reduced diet thwarts aging, disease in monkeys The bottom-line message from a decades-long study of monkeys on a restricted diet is simple: Consuming fewer calories leads to a longer, healthier life. More Spiders Current Events and Spiders News Articles |
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