A new and rare species of “giant” orb web spider has been discovered in Africa and Madagascar.
(in this pic French campaign against aids). Females are giants in newly discovered species of golden orb weaver spider. Scientists from United States and Slovenia have discovered a new species of spider that is the largest golden orb weaver spider known. Named Nephila komaci, the spider is native to Africa and Madagascar. Females of the species have a body length of 1.5 inches and a leg span of 4 to 5 inches. Males are much smaller than the females. The new spider was described and named in the Oct. 21 issue of the journal PLoS ONE by Jonathan Coddington, senior scientist and curator of arachnids and myriapods in the Department of Entomology at the Smithsonian’s National Museum of Natural History and Matjaž Kuntner, chair of the Institute of Biology of the Slovenian Academy of Sciences and Arts and a Smithsonian research associate. More than 41,000 spider species are known to science with about 400 – 500 new species added each year. But for some well-known groups, such as the giant golden orb weavers, the last new species was discovered in the 19th century. Nephila, or golden orb weaver spiders, are renowned for being the largest web-spinning spiders. They also make the largest orb webs, which can often exceed 3 feet in diameter. These spiders are also model organisms for the study of extreme sexual size dimorphism and sexual biology. Giant golden orb weavers are common throughout the tropics and subtropics. The new N. komaci species was first encountered by Kunter in the collection of the Plant Protection Research Institute in Pretoria, South Africa, in 2000.
It’s label indicated it had been collected in 1978. Kunter noticed that it did did not match any described species. Kuntner, Coddington and colleagues launched several expeditions to South Africa specifically to find this species, but all were unsuccessful, suggesting that perhaps the Nephila specimen was a hybrid or perhaps an extinct species. In 2003 the researchers encountered a second specimen, from Madagascar, in the collection of the Naturhistorisches Museum Wien in Vienna, Austria. No additional specimens turned up among more than 2,500 samples from 37 museums. The species appeared extinct until a few years ago when a South African researcher found a male and two females in Tembe Elephant Park. With this discovery, scientists became certain that the new spider was indeed a new species. In the PLoS ONE paper, Kuntner and Coddington described N. komaci as a new species, now the largest web-spinning species known, and placed it on the evolutionary tree of Nephila. Scientists believe that as Nephila spiders evolved, the females increased in size and, mainly in Africa, a group of giant spiders appeared. Nephila males, in contrast, did not grow larger over time, but remained about five times smaller than their mates. Males look like “miniatures” next to their mates, yet the males are actually normal-sized; the females are giants. Kuntner and Coddington urge the public to find new populations of N. komaci in Africa or Madagascar, both to facilitate more research on the group, but also because the species seems to be extremely rare. “We fear the species might be endangered, as its only definite habitat is a sand forest in Tembe Elephant Park in KwaZulu-Natal,” Coddington says.
“Our data suggest that the species is not abundant, its range is restricted and all known localities lie within two endangered biodiversity hotspots: Maputaland and Madagascar.” news from smithsonianscience.org – Spiders (order Araneae) are air-breathing chelicerate arthropods that have eight legs, and chelicerae modified into fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms. Spiders are found world-wide on every continent except for Antarctica, and have become established in nearly every ecological niche with the exception of air and sea colonization. As of 2008, approximately 40,000 spider species, and 109 families have been recorded by taxonomists; however, there has been confusion within the scientific community as to how all these genera should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900. Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure. Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of silk glands within their abdomen. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appear in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets.
True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving order, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic period, before 200 million years ago. A vegetarian species was described in 2008,but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders’ guts are too narrow to take solids, and they liquidize their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws. Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the aggressive widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity. While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers.
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