Golden silk spider
| Golden silk spider | ||||||||||||
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Golden silk spider (female below, male above) |
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| Scientific name | ||||||||||||
| Nephila clavipes | ||||||||||||
| ( Linnaeus , 1767) |
The golden silk spider ( Nephila clavipes ) is a species of spider found from the United States to Argentina. This spider has a very conspicuous drawing and, like all members of the genus Nephila , a pronounced sexual dimorphism : the males are much smaller than the females and less conspicuously colored.
Your silk is the subject of current research because it is extremely stable and tear-resistant. Spider webs of the related species Nephila pilipes are therefore also used as fishing nets by the local population.
features
The body length of adult females is between 2.4 and 4 cm. The female has a strikingly colored, elongated rear body ( opisthosoma ). Its basic color can vary widely, mostly it is orange or olive. The top bears ten to twelve conspicuous yellow, parallel points. The underside shows a fine network of yellow areas and bears a red mound on which the spinnerets are located. There are light spots between the light vertical stripes on the underside. They occur at least in the rear part of the underside of the opisthosoma and multiply with the age of the animal. When viewed from the side, the opisthosoma looks like a trapezoid that opens upwards . Young animals have a light-colored longitudinal band on the sternum similar to the related species Nephila clavata , which it loses with age. Indistinct spots remain. Instead, reddish spots appear on the sternum side. There are usually two distinct bumps on the front body ( prosoma ).
The legs are black and have white rings. In contrast to the subspecies N. c. fasciculata is characterized by little tufts of hair on the front two pairs of legs and on the back pair of legs, these consist only of thin, short hair. These bushy areas are missing on the third pair of legs. These legs are also much smaller than the rest. The prosoma is colored white-silver on the upper side.
As with many representatives of the family, the gender dimorphism in terms of size is enormous. The body length of the males corresponds approximately to the length of the front body of the females.
Sex organs: The rear indented part of the sexual opening of the female is more or less strongly humped. The last third of the male's globe becomes very thin.
Way of life
Network construction
The species builds fine-meshed nets that can be up to two meters in diameter. They are placed in insect flight paths, especially on the sides of forest clearings and forest paths, and over forest streams. The spider builds an off-center wheel and hides on the topmost point of the web where the threads come together, waiting for prey there. In contrast to many other orb web spiders , which regularly tear their webs down and build new ones, they mend large parts of the web and leave the rest. Ribbons to stabilize the net occur mainly in not yet fully grown animals. They also serve as a basis for moulting.
The networks are often very close to one another. However, this is not a social system, a favorable location for building a web is only used by many spiders at the same time.
Protection against overheating
The spider protects itself from overheating from a temperature of 35 ° C. To do this, she stretches her abdomen towards the sun, which increases the angle of the sun's rays. Liquid is also processed in the chelicerae, which also provides cooling. The top of the prosoma is silver, which increases light reflection and also protects the spider from overheating.
Reproduction
The species reproduces once a year. Johann Christian Fabricius assumes that females in tropical regions build a cocoon several times a year, like the related species Nephila maculata . Males can be found in the female's net between July and September.
The presence of males in a female's web depends on the size of the female spider. If the female spider is smaller than an inch, there are never males. Males are likely to be found in the net from one centimeter. Males can also be found in the network of infertile females over a length of one centimeter. This is probably due to the fact that males wait for the female to molt to maturity and thus have the best starting position for mating. Several males fight each other in a net.
The female is ready to mate 48 hours after moulting. In order not to be confused with prey by the females, the male has a typical courtship behavior . It vibrates with the opisthosoma and makes twitching movements. Mating mostly takes place in August. It is also common to find females with a later molt and mating, who do not build cocoons until late in autumn. The cocoons are 2.5 to 3 cm in diameter and each contain several hundred eggs. The cocoon is spun from curled, yellow silk.
Females die on average 27 days after moulting; Males live an average of 14 to 21 days after moulting.
Parasites
There are often up to forty thief spiders of the genus Argyrodes in the webs . These are small spiders that steal part of the prey from the silk spider.
A parasitoid is a wasp belonging to the genus Hymenoepimecis . She lays an egg on the spider's abdomen. The hatching larva sucks the spider continuously, which slowly perishes as a result.
Systematics and distribution
In addition to the nominate form, three subspecies are recognized:
- N. clavipes clavipes ( Linnaeus , 1767)
- N. clavipes fasciculata ( De Geer , 1778)
- N. clavipes vespucea ( Walckenaer , 1842)
Nephila clavipes clavipes
The distribution area of the nominate form extends from the north of the USA , the Caribbean islands and the Gulf states to the south of Argentina . It is also endemic to São Tomé .
Nephila clavipes fasciculata
The distribution area extends from north of North Carolina over Florida , the Caribbean islands and the Gulf States to the south of Argentina. The difference between this subspecies and the nominate form are the typical bushy parts on the legs and the great variability in the body length of the males, which can be 3.2 mm to 8.0 mm.
Nephila clavipes vespucea
The distribution area of this subspecies is limited to Argentina. It was first described by Charles Walckenaer as a separate species Epeira vespucea .
The differences to the features of the nominate form are as follows: The cusps on the cephalothorax are completely absent or barely rise above the skin of the back. The silver hair spots on the opisthosoma only appear on the front edge and usually converge in a closed cross-connection.
Spider silk research
The threads of the golden silk spider are being researched because they are particularly tear-resistant. It has been observed that even small birds get caught in the spider's webs, although they do not belong to the food spectrum. The spider's threads consist of one hundred percent protein . The protein molecules form a chain of crystals in the frame threads of the network, which are strung together like an accordion. This zigzag shape gives the spider silk the necessary stability. In contrast to the spider silk of most spiders, in the silk spider species and in particular in Nephila clavipes the empty spaces between this crystalline structure are not filled in a random manner . The filling has an order that additionally stabilizes the threads, but makes them less elastic. The tensile strength is therefore higher than that of nylon. Spider silk also differs from synthetic fibers in terms of its viscoelastic properties. It converts a large part of the kinetic energy into heat. This prevents prey from being "thrown out" of the net like on a trampoline.
In order to artificially produce the proteins of the spider threads, genes from the golden silk spider were transferred into bacteria at the University of British Columbia in Vancouver. In this way, these bacteria produce spider silk proteins for basic research. The scientists at the Leibniz Institute for Plant Genetics and Crop Plant Research in Gatersleben near Magdeburg took a different approach : They smuggled the genes into tobacco and potato plants . Two grams of spider silk proteins can be obtained from around a hundred tobacco plants. Since the proteins in the spider's glands are first formed into spider silk, these artificial proteins have to be processed. The Institute for Molecular Biotechnology Jena therefore takes care of the mechanical production of artificial spider silk from the artificially obtained proteins.
The aim of this research could be that the threads could be used to make ropes, seat belts, or protective clothing. In contrast to synthetic fibers, the threads are also biodegradable.
The spider proteins are also tested in medicine. At the Hannover Medical School, nerve cells were able to grow up to 6 cm in a direction along spider silk. This could increase the chances of recovery from nerve tract injuries such as paraplegia.
Web links
- Trichonephila clavipes in the World Spider Catalog
- Trichonephila clavipes fasciculata in the World Spider Catalog
- Trichonephila clavipes vespucea in the World Spider Catalog
- Description in English from the University of Florida
- Eight-legged friends work for medicine
Individual evidence
- ↑ a b N. I. Platnick: Spider catalog : Nephilidae as of 2007. The world spider catalog, version 8.0. American Museum of Natural History
- ↑ a b c d e f g h i University of Florida Institute of Food and Agriculture Sciences Golden Silk Spider ( January 21, 2009 memento in the Internet Archive ), accessed October 28, 2007
- ↑ a b c d Friedrich Dahl : Seidenspinne und Spinnenseide , In: Messages from the Zoological Museum in Berlin, Berlin 1912
- ^ A b Allen F. Archer, Studies in the Orbweaving Spiders (PDF; 2.1 MB), New York 1958
- ↑ Terrestrial and Freshwater Invertebrates ( Memento from December 16, 2007 in the Internet Archive )
- ↑ a b James Farr: Social behavior of the Golden Silk Spider, Nephila clavipes (PDF; 534 kB) , In: Journal of Arachnology 4, pp. 137-144, Florida 1977
- ^ Johann Christian Fabricius : Species insectorum exhibentes eorum differentias specificas, synonyma auctorum, loca notalia, metamorphos in adiectis observationibus, descriptionibus . Hamburg & Kiloni 1781
- ↑ a b Stephanie Morse: Nephila clavipes, golden silk spider , accessed October 31, 2007
- ↑ Ola M. Fincke, Linden Higgins and Edgar Rojas: (PDF; 933 kB) Parasitism of Nephila clavipes (Araneae, Tetragnathidae) by an ichneumonid (Hymenoptera, Polyspinctini) in Panama. ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Journal of Arachnology 18, pp. 321-329, Florida, 1990
- ↑ Natural History Museum of the Burgergemeinde Bern: World Spider Catalog Version 16.5 - Nephila clavipes clavipes . Retrieved December 12, 2015.
- ^ Matjaz Kuntner: Nomenclature of Nephilinae (Tetragnathidae) spiders and type depository information , accessed December 10, 2002
- ↑ Diemut Klärner: Molecular Design in the Spider Web , In: Neue Zürcher Zeitung , Research and Technology section , March 15, 2000, No. 63
- ^ A b Andrea Six: Useful spider webs fresh from the field , In: Tages-Anzeiger , Knowledge column , February 1, 2001, p. 46
- ^ Materials research: Hightech from the spider body , In: Handelsblatt from July 15, 2014, accessed on October 2, 2015
