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Argiope lobata Pallas, 1772 ♂♀

Argiope lobata-Güzelçamli.jpg <i><b>Testudo graeca ibera</b></i> Pallas 1814||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303215915-15dff71a-th.jpg>Thumbnails<b><i>Neoscona adianta</b></i> Walckenaer, 1802||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303114602-5718c4ca-th.jpg><i><b>Testudo graeca ibera</b></i> Pallas 1814||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303215915-15dff71a-th.jpg>Thumbnails<b><i>Neoscona adianta</b></i> Walckenaer, 1802||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303114602-5718c4ca-th.jpg><i><b>Testudo graeca ibera</b></i> Pallas 1814||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303215915-15dff71a-th.jpg>Thumbnails<b><i>Neoscona adianta</b></i> Walckenaer, 1802||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303114602-5718c4ca-th.jpg><i><b>Testudo graeca ibera</b></i> Pallas 1814||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303215915-15dff71a-th.jpg>Thumbnails<b><i>Neoscona adianta</b></i> Walckenaer, 1802||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303114602-5718c4ca-th.jpg><i><b>Testudo graeca ibera</b></i> Pallas 1814||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303215915-15dff71a-th.jpg>Thumbnails<b><i>Neoscona adianta</b></i> Walckenaer, 1802||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303114602-5718c4ca-th.jpg><i><b>Testudo graeca ibera</b></i> Pallas 1814||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303215915-15dff71a-th.jpg>Thumbnails<b><i>Neoscona adianta</b></i> Walckenaer, 1802||<img src=./_datas/t/6/y/t6ynvw9sux/i/uploads/t/6/y/t6ynvw9sux//2012/03/03/20120303114602-5718c4ca-th.jpg>

Argiope lobata Pallas, 1772 ♂♀
Common names : Lobed Argiope [En], Argiope lobée, Argiope soyeuse [Fr].

Güzelçamlı, AYDIN ● Turkey

Description: The male of this species is small (body length 6 mm) but the female is large and spectacular at up to 25 mm in length. The silver abdomen is marked with black and red spots and carries deep furrows and distinctive lobes around the edge.

Biology: As with other spiders in this genus, the large web is usually decorated with prominent zig-zag stabilimenta. The stabilimenta have been accredited with several possible functions including: to make the web more visible and so avoid damage by passing animals or to reflect ultraviolet light which attracts insects.
Once suitable prey has hit the web it will be wrapped in silk to immobilize it and then bitten to inject venom. This venom will paralyze the victim and also begin to liquefy the insides with protein dissolving enzymes. When the food parcel stops struggling the spider can suck out the juices and then discard the silk covered remains. If not eaten immediately it can be stored for later consumption. If the caught prey is too large it will be cut it free from the web.
The adult female is around three times larger than the male. The male will approach a female when she has just completed her final moult. This is when she reaches sexual maturity but also a moment when he is least likely to be eaten. Once mating is completed the male will retreat. The female gradually expands, heavy with eggs and around one month later she will lay several egg sacs in nearby vegetation.
The venom is not dangerous to humans. In the very unlikely case of a bite occurring there may be mild swelling and itching.

Sexual cannibalism and Genital damage: Sperm competition is a potent driving force in evolution leading to a remarkable variety of male adaptations that prevent or reduce fertilisation by rivals. An extraordinary defensive strategy against sperm competition has evolved in a number of web spiders where males break off parts of their paired genitalia in order to obstruct the copulatory openings of females (=mating plug). A recent comparative analysis on the family level reports that genital damage is most frequent in species with sexual cannibalism although as yet a functional association between sexual cannibalism and genital damage has not been found. Using the moderately sexually cannibalistic orb-web spider Argiope lobata we show for the first time, that males cannibalized during their first copulation damaged their pedipalps with significantly higher probability (74%) than males that escaped (15%). Of all males that damaged their genitalia, 44% were able to place a genital fragment inside the copulatory opening of the female, resulting in a relatively low total plugging rate of 14%. Successful obstruction of the female copulatory opening reduced the share of paternity of subsequent males (P2=0.06%), thus indicating that genital damage may have evolved as a response to sperm competition in this species as well. However, the low incidence of successful plugging and the strong relationship between sexual cannibalism and genital damage suggest that apart from paternity protection, the nature of genital damage in A. lobata is further shaped by sexual conflict or cryptic female choice.

Distribution: Africa, southern Europe and Asia.

References:
Wikipedia, Argiope lobata
Wildside Holidays
Nessler S.H., Uhl G., Schneider J., 2008. Sexual cannibalism facilitates genital damage in Argiope lobata (Araneae: Araneidae), Behavioral Ecology and Sociobiology, DOI 10.1007/s00265-008-0669-2



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Tuesday 5 July 2011
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