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1 November 2012 Nephila female gigantism attained through post-maturity molting
Matjaž Kuntner, Shichang Zhang, Matjaž Gregorič, Daiqin Li
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Nephila are known for the greatest degrees of sexual size dimorphism among orb weaving spiders (Araneoidea) and thus among terrestrial animals. However, a meaningful quantification of the dimorphism is lacking and the proximate developmental mechanisms of female gigantism are poorly understood, being attributed solely to female delayed maturation. Here we show that females in the giant wood spider Nephila pilipes (Fabricius 1793) become giants through facultative post-maturity molting, a phenomenon resulting in female carapaces on average 4.27 times longer than males' (ranging from 3 to 6.4 times), and female mass averaging 125 times the male's (ranging from 28 to 502 times). Although the small males follow a typical developmental pathway and reach maturity with their final molt, the females mature at varying sizes and instars and then continue to grow by molting the entire exoskeleton except their genitals. The newly discovered phenomenon of additional, single-sex, adult, non-genital molting may represent a critical developmental adaptation that facilitates female gigantism in Nephila as a response to fecundity selection.

Matjaž Kuntner, Shichang Zhang, Matjaž Gregorič, and Daiqin Li "Nephila female gigantism attained through post-maturity molting," The Journal of Arachnology 40(3), 345-347, (1 November 2012).
Received: 8 February 2012; Published: 1 November 2012
fecundity selection
Nephila pilipes
sexual size dimorphism
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