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Golden Orb-Web Spider at La Selva


Nephila clavipes
Golden Orb-Web Spider

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Ricky Layson, Ricky Layson Photography, Bugwood.org






Class: Arachnida
Order: Araneae
Family: Nephilidae
Genus: Nephila
Spanish Name: Arana de oro


Distribution, Range, and Abundance:

The Nephila clavipes belongs to a genus of spiders that is normal distributed all throughout the world including parts of Asia, Africa, China, and India. This individual species is the only member of the genus that is found in the Western Hemisphere. This species range occurs as far north as North Carolina, throughout Florida, across the Gulf States, through Central America, and all the way south as Argentina. This spider is one of the more prominent species found at La Selva biological station.
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Golden Orb-Web Spider web at La Selva


Habitat and Web Formations:Nephila clavipes typically builds and domesticates webs that are made in open woods or at the edges of dense forests. Many times webs will be congregated near one and other especially in times after summer and before fall. Males and females typically congregate within one web for hub position (which is beneficial for food capture). T
he largest male usually gains exclusive mating rights and the other smaller males typically forage around different webs looking for a female to mate with. Webs are typically large and complex and have to be repaired frequently. Females have the opportunity to invest highly within their webs since they are the most important source of food and survival for the spiders.(COTERC)
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Golden Orb-Web Spider from afar at La Selva






Coloration and Morphology: Between male and female golden orb spiders (and within the Nephila genus ovrall) there is a very large sexual size dimorphism. Typically, female spiders can be up to 9.5 cm long from the tip of the hind leg to the tip of the front leg. Males are much smaller averaging less than 1.25 cm in length. This makes females five to six times larger than males. In terms of coloration males are less colorful typically being a dark brown color throughout their form. Females tend to have much more coloration including a golden orb structure on the posterior side of the spider. The name golden orb spider though is based off of the golden color the spider silk makes when it is flashed with sunlight. . Evolutionary analysis show that the large difference in size between males and females is based in female gigantism rather than male dwarfism (Kunter M. ,et. al. 2009). There are different hypothesis that contend the relationship between the smaller males including, sexual cannibalism (males are smaller to avoid being
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Sturgis McKeever, Georgia Southern University, Bugwood.org
eaten by the larger females), and the gravity hypothesis. The gravity hypothesis states that it is advantageous for males to be small since smaller spiders have faster climbing speeds. The faster the spider the more adapted it will be to obtaining food and finding the larger females to mate. Observations of this phenomena have been verified (Moya-Larano J. et. al., 2007) and refuted (Prenter J. et. al., 2009). In terms of defense mechanisms for male spiders. It has been observed that it is most important for males to obtain the hub of the web (the top middle) and defend it, regardless of female status, so they will have the best chance to mate (Cohn et. al 1988).

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Golden Orb-Web Spider at La Selva

Behavior:These spiders are seen as semi-sociable and it is quite common to see different individuals using other spiders web lines as a bases for their own. As long as their is food available to their spiders then they will love collectively. The spiders do posses venom that is not lethal to humans but is very potent. They tend to bite when stirred or disrupted and rarely are aggressive if not provoked. These800px-Nephila_clavipes_-_Merritt_Island_NWR_Floida.jpg spider typically obtain their food by foraging their webs for captured prey. Foraging is a very important behavioral characteristic of the golden orb web spider and is completely dependent on web placement. The hub of the web is where the female spider typically resides. The main orb can sometimes reach one meter in width and is typically surrounded by security silk strands around the outside of the web. These security strands are typically there to function as a barrier web so birds do not plunder through the entire structure. These secondary webs also send vibrations to the female spider when prey is captured. The tensile strength of the spiders silk is 4x10^9 N/m^2 which is stronger than steel by a factor of six (Spooner, A. et. al. 2007). Males typically abandon their web making abilities as the grow older and rely completely on the female to create a web and capture food. In terms of reproduction, males will typically have to sneak up on females (usually when they are feeding) to begin the reproductive process (Brown, S.G. 1985 and Christensen et.al 1985).
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Golden Orb-Web Spider Missing Two Legs at La Selva

Diet and Species Interaction:The Golden Orb-Web Spider's diet typically consists of flying insects that are caught in the web of the spiders. The webs are created to best exploit the flight patterns of insects. Flies, bees, wasps, small moths, and butterflies are the typical prey of the spiders and females have also been observed feeding on large beetles and even other male spiders (Schneider et. al 2000). N. clavipes are routinely preyed upon and victimized by Argyrodes a kleptoparasitic family of spiders that infest the golden orb spiders web and feed on the food they capture and on male spiders. N. clavipes will routinely have to rebuild or move their home webs in order to compensate for Argyrode infestation because detection of theft in such a large we
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Chris Evans, River to River CWMA, Bugwood.org
b would be difficult for the N. clavipes.
'

Observations at La Selva:
Nephila clavipes is supposedly one of the more abundant spiders at La Selva but during our stay I only saw one spider and it was a juvenile. From this one specimen I did gather some valuable information that backs some of the literature I read on the subject. Most importantly, I observed the tensile strength of the golden orb-web spider's web. 1333008.jpgIt can be compared to a guitar string when plucked and it was almost impossible to tear or rip on my own. Secondly, the one spider that I observed was missing two of its hind legs leaving it almost immobilized in its web. Literature on the spider stated that there are common predators to the golden orb-web spider and that attacks occur very regularly. My best guess says that the spider I observed was attacked by a predator and more than likely it was another spider probably from the Argyrodes family.
References:

S. G. Brown, Mating behavior of the golden orb-weaving spider, Nephila clavipes: II. Sperm capacitation, sperm competition, and fecundity. Journal of Comparative Psychology 99 (1985), pp. 167–175.

Canadian Organization for Tropical Education and Rainforest Conservation (COTERC) http://www.coterc.org/documents/InfoSheetGoldenSilkSpider.pdf 2007.


Christenson T. E, S. G. Brown, P. A. Wenzl, E. M. Hill and K. C. Goist, Mating behavior of the golden-orb-weaving spider, Nephila clavipes: I. Female receptivity and male courtship. Journal of Comparative Psychology 99 (1985), pp. 160–166

Cohn, Jeffrey; Balding, Frances V.; Christenson, Terry E. In Defense of Nephila clavipes: Postmate guarding by the male golden orb-weaving spider. Journal of Comparative Psychology. Vol 102(4), Dec 1988, 319-325. doi:

Kuntner M, Coddington JA (2009) Discovery of the Largest Orbweaving Spider Species: The Evolution of Gigantism in Nephila. PLoS ONE 4(10): e7516.doi:10.1371/journal.pone.0007516

Moya-Laran˜o J, Vinkovic´ D, Allard CM, Foellmer MW (2009) Optimal climbing speed explains the evolution of extreme sexual size dimorphism in spiders. Journal of Evolutionary Biology 22: 954–963.

Prenter, J., Pérez-Staples, D. & Taylor, P.W. The effects of morphology and substrate diameter on climbing and locomotor performance in male spiders. Functional Ecology.

Schneider, Jutta M., and Mark A. Elgar. "Sexual Cannibalism and Sperm Competition in the Golden Orb-web Spider Nephila plumipes (Araneoidea); Female and Male Persepctives." Behavioral Ecology 12.5 (2000): 547-52. Oxford Journals. Web. 18 April. 2010. <http://beheco.oxfordjournals.org/cgi/content/full/12/5/547>.

Sponner A, Vater W, Monajembashi S, Unger E, Grosse F, et al (2007) Composition and Hierarchical Organisation of a Spider Silk. PLoSONE 2(10): e998. doi:10.1371/journal.pone.0000998