Nephila clavipes and maculata
The Nephila species (Figs. 5-9) have a very much stronger chelicerai m.antero-medialis verticalis than Azilia and thus resemble the Araneidae earlier dissected by me. N.clavipes has a cleft suspensor IV,. N.maculata a single one; this feature is apparently of little taxonomic value.
The anterior tergo-pedipalpal muscle [pa) is double-fanned in N. clavipes , but triple-fanned in.AT. maculata . The m. tergo-coxalis anterior profundus (c,, "anterior rotator") of the first leg arises in JV. clavipes as two broad portions; in N.maculata one of the portions is very narrow. None of the Nephila species has caecal pouches protruding between the tergo-coxal muscles. In JV clavipes the dorsal pouch is short. In JV. maculala it extends to the base of the chelicerae and sends a very narrow tube into them, a feature reminiscent of the Tetragnathidae . In this species the poison gland is short, while in JV. clavipes it extends to the dorsal apodeme. I have previously drawn attention to the apparent competition for space between the poison glands and the dorsal caecum.
- Palmgren, P. (1980): Some comments on the anatomy of spiders. Ann. Zool. Fennici 17, 161-173: 162-162, URL:http://antbase.org/ants/publications/Palmgren1980/Palmgren1980.pdf
N. clavipes are highly sexually dimorphic. Females are significantly larger than males ranging from 5 to 6 times the size of the male. Generally, females are 3 inches long. Newly hatched golden silk spiders weigh 0.07g and adult females weigh 4g. They are mostly yellow with an elongated abdomen and long, hairy legs (Higgens 1992).
Other Physical Features: ectothermic ; bilateral symmetry
Golden web spiders are found in areas of high humidity and relatively open space. They live in forest areas along trails and clearing edges (Vargas 1997).
Terrestrial Biomes: forest
N. clavipes feed on small flying insects. Webs constructed by golden silk spiders are used to catch this prey. They can feed on grasshoppers, flies, and other small insects. As the prey is entangled in the strong web, N. clavipes wrap it in silk like a casing.
Life History and Behavior
Approximately four days before females reach a final molt, they cease web reparation and prey capture. Females are sexually receptive for 48 hours after their final molt has occured. For reproduction to occur among N. clavipes, males must stimulate females and arouse them in order to prevent from becoming prey. Although, in this species of spider, predation on males is not a common occurence. When males approach females for copulation, males vibrate their abdomen and uses a plucking motion. This activity varies depending on the age of females. Once the sperm is transfered, it is stored in the spermathecae. After copulation, females can change web-sites and male partners throughout their adulthood.
After the final molt, females can live 27 days, while males live from 14-21 (Christenson 1985, Brown 1985).
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)
Evolution and Systematics
The web glue that coats silk threads of orb weaving spider webs has incredible adhesive strength thanks to glycoproteins.
"The various silks that make up the web of the orb web spiders have been studied extensively. However, success in prey capture depends as much on the web glue as on the fibers. Spider silk glue, which is considered one of the strongest and most effective biological glues, is an aqueous solution secreted from the orb weaving spider's aggregate glands and coats the spiral prey capturing threads of their webs. Studies identified the major component of the glue as microscopic nodules made of a glycoprotein. This study describes two newly discovered proteins that form the glue-glycoprotein of the golden orb weaving spider Nephila clavipes. Our results demonstrate that both proteins contain unique 110 amino acid repetitive domains that are encoded by opposite strands of the same DNA sequence. Thus, the genome of the spider encodes two distinct yet functionally related genes by using both strands of an identical DNA sequence. Moreover, the closest match for the nonrepetitive region of one of the proteins is chitin binding proteins. The web glue appears to have evolved a substantial level of sophistication matching that of the spider silk fibers." (Choresh et al. 2009:2852)
"Biological materials function in environments where seasonal and even daily changes in conditions have the potential to alter the properties and performance of these materials. This study is the first to examine how changes in environmental humidity affect the extensibility of droplets, which are responsible for the adhesion of viscous capture threads that are produced by over 4000 species of orb-weaving spiders in the Araneoidea clade. These threads form an orb web’s sticky prey capture spiral, which retains insects that strike the web, providing a spider with more time to locate and subdue their prey. Viscous threads are comprised of small, regularly spaced aqueous droplets that surround a pair of supporting axial fibers and are produced by a triad of spigots on each of a spider’s paired posterior spinnerets. The single flagelliform gland spigot of this triad produces an axial fiber and is flanked by two aggregate gland spigots, which coat this fiber with aqueous material. The coated axial fibers merge to form a contiguous pair of fibers surrounded initially by a sheath of viscous material. As a thread absorbs atmospheric moisture in the high humidity of the early morning hours, this material quickly condenses into a regular series of droplets whose size and spacing differ greatly among species.
"The glycoprotein within each droplet that confers thread adhesion is encoded by two genes. The asg1 gene produces a 406-amino-acid protein, whose upstream region has a high proportion of charged amino acids, which are considered hydrophilic, and its repeating downstream region is similar to mucin, known to have adhesive properties. The asg2 gene produces a 714-amino-acid protein, whose upstream region is similar to known chitin-binding proteins, adapting it to adhere to insect exoskeleton, whereas its repeating downstream region has high proline content that resembles that of elastin and flagelliform spider silk, making it elastic. This combination of features confers adhesion, extensibility and hygroscopicity to the glycoprotein–crucial and complementary properties in the context viscous thread performance." (Opell et al. 2011:2988)
Learn more about this functional adaptation.
- 2009. Spider web glue spins society toward new biobased adhesives. EurekAlert! [Internet],
- Choresh O; Bayarmagnae B; Lewis RV. 2009. Spider web glue: two proteins expressed from opposite strands of the same DNA sequence. Biomacromolecules. 10(10): 2852–2856.
- Opell BD; Karinshak SE; Sigler MA. 2011. Humidity affects the extensibility of an orb-weaving spider’s viscous thread droplets. The Journal of Experimental Biology. 214(17): 2988-2993.
Dragline silk fibers in spider webs help maintain web tension under weight by contracting and relaxing in response to humidity.
"The abrupt halt of a bumble bee's flight when it impacts the almost invisible threads of an orb web provides an elegant example of the amazing strength and toughness of spider silk. Spiders depend upon these properties for survival, yet the impressive performance of silk is not limited solely to tensile mechanics. Here, we show that silk also exhibits powerful cyclic contractions, allowing it to act as a high performance mimic of biological muscles. These contractions are actuated by changes in humidity alone and repeatedly generate work 50 times greater than the equivalent mass of human muscle. Although we demonstrate that this response is general and occurs weakly in diverse hydrophilic materials, the high modulus of spider silk is such that it generates exceptional force. Furthermore, because this effect already operates at the level of single silk fibers, only 5 µm in diameter, it can easily be scaled across the entire size range at which biological muscles operate. By contrast, the most successful synthetic muscles developed so far are driven by electric voltage, such that they cannot scale easily across large ranges in cross-sectional areas. The potential applicability of silk muscles is further enhanced by our finding that silkworm fibers also exhibit cyclic contraction because they are already available in commercial quantities. The simplicity of using wet or dry air to drive the biomimetic silk muscle fibers and the incredible power generated by silk offer unique possibilities in designing lightweight and compact actuators for robots and micro-machines, new sensors, and green energy production." (Agnarsson et al. 2009:1990)
"Spider dragline silk is a model biological polymer for biomimetic research due to its many desirable and unusual properties. 'Supercontraction' describes the dramatic shrinking of dragline silk fibers when wetted. In restrained silk fibers, supercontraction generates substantial stresses of 40–50 MPa above a critical humidity of ~70% relative humidity (RH). This stress may maintain tension in webs under the weight of rain or dew and could be used in industry for robotics, sensor technology, and other applications. Our own findings indicate that supercontraction can generate stress over a much broader range than previously reported, from 10 to 140 MPa. Here we show that this variation in supercontraction stress depends upon the rate at which the environment reaches the critical level of humidity causing supercontraction. Slow humidity increase, over several minutes, leads to relatively low supercontraction stress, while fast humidity increase, over a few seconds, typically results in higher supercontraction stress. Slowly supercontracted fibers take up less water and differ in thermostability from rapidly supercontracted fibers, as shown by thermogravimetric analysis. This suggests that spider silk achieves different molecular configurations depending upon the speed at which supercontraction occurs. Ultimately, rate-dependent supercontraction may provide a mechanism to tailor the properties of silk or biomimetic fibers for various applications." (Agnarsson et al. 2009:325)
Learn more about this functional adaptation.
- Agnarsson I; Boutry C; Wong SC; Baji A; Dhinojwala A; Sensenig AT; Blackledge TA. 2009. Supercontraction forces in spider dragline silk depend on hydration rate. Zoology. 112(5): 325-331.
- Agnarsson I; Dhinojwala A; Sahni V; Blackledge TA. 2009. Spider silk as a novel high performance biomimetic muscle driven by humidity. Journal of Experimental Biology. 212: 1990-1994.
- Blackledge TA; Boutry C; Wong SC; Baji A; Dhinojwala A; Sahni V; Agnarsson I. 2009. How super is supercontraction? Persistent versus cyclic responses to humidity in spider dragline silk. Journal of Experimental Biology. 212: 1981-1989.
- Bland E. 2009. Spider silk used as artificial muscle. Discovery News [Internet],
Molecular Biology and Genetics
Barcode data: Nephila clavipes
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Statistics of barcoding coverage: Nephila clavipes
Public Records: 2
Specimens with Barcodes: 14
Species With Barcodes: 1
CITES: no special status
Relevance to Humans and Ecosystems
An important way in which golden silk spiders benefit humans is with the use of their dragline thread (the silk). N. clavipes, in particular, weave rather strong webs compared to other species of spiders. Currently, there are tests being done on the potential benefits of human use of the dragline thread. The dragline in golden silk spiders surpasses the strength of "Kevlar," which is a fiber used in bullet-proof vests. The dragline thread is biodegradable, stronger than steel, and economically valuable (Unger 1996).
|This article has an unclear citation style. (June 2014)|
Nephila clavipes has the large size and the long legs with clumps of hair that are typical of the genus. It is large compared to most other members of the genus, and is distinguished by the bright colours of the female abdomen, which changes colour as the spider matures.
As is usual among orb-weavers, there is marked sexual dimorphism in general appearance, but especially in size; in linear measurements males are three to four times smaller than females, and they also are more slenderly built. This implies a mass some thirty to seventy times smaller than that of a large female.
The specific epithet clavipes is derived from the Latin:
- clava, that variously may mean "knotted staff", "club", or "key"; and
- pēs meaning "of or pertaining to a foot".
In assigning the name, Linnaeus apparently referred to the clumps of hair on the legs.
Distribution and transport
Nephila clavipes occurs most commonly in the Antilles and in Central America from Mexico in the north through Panama in the south. Less abundantly it occurs as far south as Argentina and in the north it occurs in parts of the southern states of the continental USA. Seasonally it may range more widely; in summer it may be found as far north as lower Eastern Canada. Beyond 40° N latitude these spiders seldom survive the winter.
Because humans inadvertently transport spiders as passengers in cargo containers, plant nursery stock and the like, Nephila clavipes generally occurs very unevenly over wide areas; often there are patches of high local densities far from any other populations. Accidental human transport of the species increases markedly in late August to early September, when the spiders' reproduction is at its height.
The main web of a mature female may be as large as one meter in diameter, not counting the main filaments that anchor the web between trees; such anchor filaments may be two or three meters in length. A yellow pigment in the silk lends it a rich golden glow in suitable lighting. Males come into the female's web for copulation and mate with her while she is feeding and unable to attack them. After mating, the female spins an egg sac on a tree, laying hundreds of eggs in each sac.
Significance to humans
The spider is not aggressive and only bites if pinched; the venom is relatively harmless and rarely causes more than slight redness and temporary localized pain.
The silk of Nephila clavipes has recently been investigated to evaluate its usefulness in surgically improving mammalian neuronal regeneration. In vitro experiments showed that a filament of the silk can lead a severed neuron through the body to the site from which it was severed. Best of all for these experiments, the silk elicits no reaction from the immune system, and thereby escapes rejection by the host body.
- Allmeling, C.; Jokuszies, A.; Reimers, K.; Kall, S. & Vogt, P.M. (2006): Use of spider silk fibres as an innovative material in a biocompatible artificial nerve conduit. J. Cell. Mol. Med. 10(3): 770-777. PDF - doi:10.2755/jcmm010.003.18
- Borror, D. J. 1960. Dictionary of Word Roots and Combining Forms. Mayfield Publishing Company, 134 pp.
- Cameron, H. D. 2005. Chapter 73 — An etymological dictionary of North American spider genus names, page 73 in D. Ubick, P. Paquin, P.E. Cushing, and V. Roth (eds.) Spiders of North America: an identification manual. American Arachnological Society, Keene (New Hampshire).
- Weems, Jr., H.V., and G.B. Edwards, Jr. 2001 (2004 revision). golden silk spider. on the UF / IFAS Featured Creatures Web site
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