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Spider Personality a Communal Affair

Posted By Prucia Buscell, Thursday, May 15, 2014

Behavior and personality are strongly influenced by participation in groups, and individuals living in stable environments seem more able to develop their own distinctive styles than individuals who face frequent disruption.

That sounds like human experience, but this finding came from research on social spiders. While most of the world's 43,000 varieties of spiders work alone as they spin webs and devour prey, Stegodyphus dumicola is one of the 35 or so arachnid species that could make an arachnophobe flee in horror. These social spiders collaboratively build massive webs that allow them to capture prey bigger than they are, and they organize their activities and divide their labors. And as Natalie Angier writes in a New York Times story, research on these unusual creatures may provide fresh insights into such human mysteries as where personality comes from and why some individuals are innately shy while others are naturally aggressive. Jonathan N. Pruitt, PhD, a biologist at the University of Pittsburgh, who studies social spiders, told Angier, "It's very satisfying to me that the most maligned of organisms may have something to tell us about who we are."

People and animals differ hugely in such traits as shyness, boldness, and adventurousness. Writing in the Proceedings of the Royal Society B, Dr. Pruitt and Kate Laskowski, of the Leibnitz Institute of Freshwater Ecology and Inland Fisheries in Berlin, report that social spiders display individual predispositions early. Further, spiders living in a stable, predictable environment didn't become conformists. They became more individualistic and had more pronounced personal quirks than spiders that were experimentally shifted from one group to another. And personality tended to dictate how labor was divided.

Angier explains that among honeybees, caste depends on age-the youngest tend the young, while older bees forage for food and defend the hive. Ants wind up as soldiers or workers depending on their nutrition when they are larvae. Social spiders find their niche in community operations based on such individual characteristics as size and temperament.

Dr. Pruitt and colleagues found that, the innately aggressive spiders were in charge of capturing prey and defending the colony while more docile spiders tended the young. How do you discover spider personality? In one method the Times story describes, researchers puffed air at the spiders through a bulb-topped syringe. The bold ones bounced back from the perceived threat in five or fewer seconds, while the more timid ones took 10 seconds or longer. And the stable groups had the greatest variety of bold and shy. Researchers even found that whole colonies can have distinctive personalities, just as human neighborhoods can.

Scientists are discovering more and more animals that have traits we once considered exclusively human. So we can marvel at spider individuality. We can also be glad we don't share the Stegodyphus approach to family life. The father spiders commit infanticide and the mothers are suicidal. Females attach their egg cocoons to the web and guard them until babies hatch. Male Stegodyphus spiders like to steal the eggs, forcing the female to replace the cocoon and use the miscreant's sperm to fertilize at least some of her eggs. Once the babies hatch, the mother feeds her young by regurgitating most of her own meals directly into their mouths. When the babies are about a month old, they attack the mother, injecting her with their venom and digestive enzymes, and eat her. When she is consumed, the siblings cannibalize as many of their brothers and sisters as they can before the survivors embark on new lives. Read the Times story here.

left image by Dr VB Whitehead

Tags:  buscell  complexity matters  nature 

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