Hungry spiders spin deadlier webs
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Hungry black widow spiders spin webs with sticky strands to capture prey (top) while sated spiders spin more robust webs that provide better protection from predators (bottom) SOURCE: ASSOCIATION FOR THE STUDY OF ANIMAL BEHAVIOUR HUNGRY SATED Strands covered in sticky droplets GETTY THE deep ocean continues to surprise: it appears a volcano on the seabed has exploded with a force thought impossible. In 1999, the largest-ever swarm of quakes was recorded on a mid- ocean plate boundary, on the Gakkel Ridge in the east Arctic basin. To find out what caused it, Robert Sohn of the Woods Hole Oceanographic Institution, Massachusetts, and colleagues peeked at the ridge with a remote- controlled device. They found shattered rock spread over 10 square kilometres, suggesting a series of volcanic explosions (Nature, vol 453, p 1236). Such explosions can occur in shallow water if the water rapidly vaporises, but beyond 3 kilometres down the pressure is too high. Sohn reckons the magma must have contained up to 100 times more carbon dioxide than thought possible. This separated out as the magma rose and built up in a chamber beneath the seabed. Eventually the roof cracked and the CO 2 and magma burst out. “It opens the door to a lot of things that we didn’t suspect could happen,” says David Clague of the Monterey Bay Aquarium Research Institute in California. Explosion defies ocean pressure GIRLS are no less competitive than boys, they’re simply subtler about it, a study of pre-schoolers suggests. While boys use head-on aggression to get what they want, girls rely on the pain of social exclusion. To test the apparent differences in how very young children compete, Joyce Benenson at Emmanuel College in Boston and her colleagues divided 87 4-year-olds into same-sex groups of three. In successive trials, each trio received one, two or three highly prized animal puppets. The sexes behaved similarly when there were two or three puppets to go round. The differences became clear, though, when there was just one puppet for each group. Boys tended to ask for the puppet, grab at it, or even chase the child who had it. By contrast, girls punished the puppet-holder by excluding her from their clique, whispering behind her back or even hiding from her (Animal Behaviour, DOI: 10.1016/j.anbehav.2008.01.027). Benenson says that these socially aggressive tactics may account for why girls exhibit greater jealousy over same-sex friendships than boys. They could be trying to protect themselves against exclusive coalitions. Melissa Emery Thompson at the University of New Mexico in Albuquerque says the results help to dispel the myth that females are the less competitive sex. Even at an early age, they avoid risky direct aggression in favour of subtler forms of competition such as small shifts in tone and expression, or spreading rumours. Who ever said that girls aren’t competitive? BLACK widow spiders vary their webs to suit their purpose. A hungry spider spins a deadlier web, while a full one builds a fortress. Spiders that were fed daily with crickets spun tangled masses of non-sticky silk, Jacquelyn Zevenbergen and Todd Blackledge at the University of Akron, Ohio, found. But similar-size spiders that had been starved for a week tended to spin sheets of silk connected to the ground by taut, sticky strands. When an insect blunders into these strands, they detach from the ground and spring upwards, suspending the prey in mid-air. The sheet-like webs are better at transmitting the vibrations of passing prey and also make it easier for the spider to manoeuvre. The researchers found that all spiders, regardless of their condition, caught more prey more quickly and efficiently when they placed them on the webs spun by hungry individuals (Animal Behavior, DOI: 10.1016/j. anbehav.2008.05.008). Blackledge suggests that sated spiders opt to spin tangled, non- sticky webs because they provide better protection from predators. This type of purposeful alteration to web design is unique to black widows. “Their webs aren’t simply more or less of the same thing,” he says. “They are adding and deleting architectural features that have specific functions.” What a varied web they weave NATURE and nurture both play a role in eczema, but few genes have been linked to specific environmental risks. Now a gene mutation that predisposes youngsters to the skin condition seems to pose a greater risk if they are also exposed to cats. In 2006, a mutation in the gene for the protein filaggrin – which keeps foreign substances out of the skin – was shown to increase the risk of eczema. About 9 per cent of people of European origin carry this mutation. To find out whether an environmental trigger might also play a role, a team led by Hans Bisgaard of the Gentofte University Hospital in Copenhagen, Denmark, who was also involved in the 2006 work, tracked 358 Danish and 460 British children from birth. About 25 per cent of children without the mutation developed eczema, compared with 45 per cent of those with the mutation. However, of the 16 children who both had the mutation and lived with a cat, 14 developed eczema, all between the ages of 1 and 3 months (PLoS Medicine, DOI: 10.1371/journal. pmed.0050131). Bisgaard says it is too early to issue a warning to parents. Natalija Novak, a dermatologist at the University of Bonn in Germany, says we should now look for other environmental factors that correlate with eczema. I ain’t got the genes to be around cats www.newscientist.com 28 June 2008 | NewScientist | 21
Transcript of Hungry spiders spin deadlier webs
Hungry black widow spiders spin webs with sticky strands to capture prey (top) while sated spiders spin more robust webs that provide better protection from predators (bottom)
SOU
RCE
: A
SSO
CIAT
ION
FO
R T
HE
STU
DY
OF
AN
IMAL
BEH
AVIO
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HUNGRY
SATED
Strandscovered insticky droplets
GET
TY
THE deep ocean continues to surprise: it appears a volcano on the seabed has exploded with a force thought impossible.
In 1999, the largest-ever swarm of quakes was recorded on a mid-ocean plate boundary, on the Gakkel Ridge in the east Arctic basin.
To find out what caused it, Robert Sohn of the Woods Hole Oceanographic Institution, Massachusetts, and colleagues peeked at the ridge with a remote-controlled device. They found shattered rock spread over 10 square kilometres, suggesting a series of volcanic explosions (Nature, vol 453, p 1236).
Such explosions can occur in shallow water if the water rapidly vaporises, but beyond 3 kilometres down the pressure is too high. Sohn reckons the magma must have contained up to 100 times more carbon dioxide than thought possible. This separated out as the magma rose and built up in a chamber beneath the seabed. Eventually the roof cracked and the CO2 and magma burst out.
“It opens the door to a lot of things that we didn’t suspect could happen,” says David Clague of the Monterey Bay Aquarium Research Institute in California.
Explosion defies ocean pressure
GIRLS are no less competitive than boys, they’re simply subtler about it, a study of pre-schoolers suggests. While boys use head-on aggression to get what they want, girls rely on the pain of social exclusion.
To test the apparent differences in how very young children compete, Joyce Benenson at Emmanuel College in Boston and her colleagues divided 87 4-year-olds into same-sex groups of three. In successive trials, each trio received one, two or three highly prized animal puppets.
The sexes behaved similarly when there were two or three puppets to go round. The differences became clear, though, when there was just one puppet for each group. Boys tended to ask for the puppet, grab at it, or even chase the child who had it. By contrast, girls punished the puppet-holder by excluding her from their clique, whispering behind her back or even hiding from her (Animal Behaviour, DOI: 10.1016/j.anbehav.2008.01.027).
Benenson says that these socially aggressive tactics may
account for why girls exhibit greater jealousy over same-sex friendships than boys. They could be trying to protect themselves against exclusive coalitions.
Melissa Emery Thompson at the University of New Mexico in Albuquerque says the results help to dispel the myth that females are the less competitive sex. Even at an early age, they avoid risky direct aggression in favour of subtler forms of competition such as small shifts in tone and expression, or spreading rumours.
Who ever said that girls aren’t competitive?
BLACK widow spiders vary their webs to suit their purpose. A hungry spider spins a deadlier web, while a full one builds a fortress.
Spiders that were fed daily with crickets spun tangled masses of non-sticky silk, Jacquelyn Zevenbergen and Todd Blackledge at the University of Akron, Ohio, found. But similar-size spiders that had been starved for a week tended to spin sheets of silk connected to the ground by taut, sticky strands. When an insect blunders into these strands, they detach from the ground and spring upwards, suspending the prey in mid-air.
The sheet-like webs are better at transmitting the vibrations of passing prey and also make it easier for the spider to manoeuvre. The researchers found that all spiders, regardless of their condition, caught more prey more quickly and efficiently when they placed them on the webs spun by hungry individuals (Animal Behavior, DOI: 10.1016/j.anbehav.2008.05.008).
Blackledge suggests that sated spiders opt to spin tangled, non-sticky webs because they provide better protection from predators. This type of purposeful alteration to web design is unique to black widows. “Their webs aren’t simply more or less of the same thing,” he says. “They are adding and deleting architectural features that have specific functions.”
What a varied web they weave
NATURE and nurture both play a role in eczema , but few genes have been linked to specific environmental risks. Now a gene mutation that predisposes youngsters to the skin condition seems to pose a greater risk if they are also exposed to cats.
In 2006, a mutation in the gene for the protein filaggrin – which keeps foreign substances out of the skin – was shown to increase the risk of eczema. About 9 per cent of people of European origin carry this mutation.
To find out whether an environmental trigger might also play a role, a team led by Hans Bisgaard of
the Gentofte University Hospital in Copenhagen, Denmark, who was also involved in the 2006 work, tracked 358 Danish and 460 British children from birth. About 25 per cent of children without the mutation developed eczema, compared with 45 per cent of those with the mutation. However, of the 16 children who both had the mutation and lived with a cat, 14 developed eczema, all between the ages of 1 and 3 months (PLoS
Medicine, DOI: 10.1371/journal.pmed.0050131 ).
Bisgaard says it is too early to issue a warning to parents. Natalija Novak, a dermatologist at the University of Bonn in Germany, says we should now look for other environmental factors that correlate with eczema.
I ain’t got the genes to be around cats
www.newscientist.com 28 June 2008 | NewScientist | 21
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