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How the seahorse gained its shapely body
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PEOPLE with busy lives don’t necessarily live longer, but they might feel as if they do. Our brains use the world around us to keep track of time, and the more there is going on, the slower time feels. Brains were thought to measure time by using some kind of internal clock that generates events at a relatively regular rate. To test whether external stimuli might also play a role in our ability to process time, Misha Ahrens and Maneesh Sahani at University College London showed 20 subjects a video of either a randomly changing stimulus – statistically modelled on the way that things naturally change randomly in the world around us – or a static image, for a set period of time. When asked to judge how much time had passed, the volunteers who had been shown the moving stimulus were significantly more accurate. The subjects were also shown the video at two different speeds and asked to r ate the duration of each clip. They thought both clips lasted the same amount of time, even though the faster version was shorter (Current Biology, DOI: 10.1016/j. cub.2010.12.043). The results suggest that the brain exploits changes in visual information, when it’s available, to judge time, says Sahani.
Bug to spider: I will control your offspring’s sex FAMED for their ruthless reproductive strategies, female spiders are in fact mere puppets in the hands of a parasitic bug that kills off their embryonic sons. Wolbachia bacteria infect up to two-thirds of insect species. They are transmitted through eggs, and so need their host to have as many females as possible. As a result, the bacteria have evolved a bag of dirty tricks to maximise their chances of making it to the next generation. The parasite can drive their hosts to virgin births, which result
in females only, gender-bend lads into ladies or simply kill males early in development. But until now nobody knew if Wolbachia could wreak havoc on spiders too. Bram Vanthournout at Ghent University in Belgium and colleagues have found that infected female dwarf spiders produce more females than those without Wolbachia. Giving the spiders antibiotics restored a normal sex ratio, proving that the previous female bias really was Wolbachia’s work (BMC
Evolutionary Biology, DOI: 10.1186/1471-2148-11-15). Because female-dominated clutches were smaller, the researchers suspect that the bugs kill off males long before birth. Vanthournout reckons that the bacteria may also be behind virgin births, which could even give spiders an evolutionary advantage. “Some social spiders need very few males, so male competition is high,” he says. Wolbachia might spare females the trouble of producing males who will never mate. George Grall/ngs/getty
Time stretches if you keep busy
Self-controlled kid, successful adult CHILDREN who lack self-control are more likely to become adults with poor health and finances. So say Avshalom Caspi at Duke University in North Carolina, Terrie Moffitt at King’s College London and colleagues, who followed the progress of 1000 children born between 1972 and 1973 in New Zealand. The team measured self-control by asking the children, as well as their parents and teachers, about their behaviour every two years between the ages of 3 and 15, and then at 18, 21, 26 and 32. Children with higher levels of self-control were more likely to have a higher socioeconomic background and a higher IQ. After adjusting for both factors, the team found that adults who had low self-control as children were more likely to be overweight, have substance abuse problems, gum disease and sexually transmitted infections. They were also less likely to be homeowners, and more likely to have been convicted of a criminal offence (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1010076108). The team suggests governments should employ policies to target self-control in children.
How the seahorse gained its shape IT IS easy to forget that the seahorse is a fish. With its equine head, pot belly and prehensile tail, it rivals the platypus in its peculiarity. But the seahorse’s form is not just for show: its arched neck acts like a spring that stores energy, ensuring it is ready to strike when it spots a meal. Biologist Sam Van Wassenbergh at the University of Antwerp, Belgium, and colleagues created mathematical models based on the body shape of seahorses and their straight-bodied cousins, pipefish. The models revealed that seahorses’ necks have the elasticity and stability
needed to let them lunge forward and grab a passing shrimp, even if it is some distance away. Pipefish, in contrast, cannot strike out so far and must settle for closer prey. This bend and snap technique is a vital hunting method for most seahorse species, as they are weak swimmers (Nature Communications, DOI: 10.1038/ncomms1168). “Like everyone, I have always wondered why seahorses look so bizarre,” says Adam Jones at Texas A&M University in College Station. “This is the first step in establishing it’s an adaptation.”
29 January 2011 | NewScientist | 15
sot/stone+/getty
PEOPLE with busy lives don’t necessarily live longer, but they might feel as if they do. Our brains use the world around us to keep track of time, and the more there is going on, the slower time feels. Brains were thought to measure time by using some kind of internal clock that generates events at a relatively regular rate. To test whether external stimuli might also play a role in our ability to process time, Misha Ahrens and Maneesh Sahani at University College London showed 20 subjects a video of either a randomly changing stimulus – statistically modelled on the way that things naturally change randomly in the world around us – or a static image, for a set period of time. When asked to judge how much time had passed, the volunteers who had been shown the moving stimulus were significantly more accurate. The subjects were also shown the video at two different speeds and asked to r ate the duration of each clip. They thought both clips lasted the same amount of time, even though the faster version was shorter (Current Biology, DOI: 10.1016/j. cub.2010.12.043). The results suggest that the brain exploits changes in visual information, when it’s available, to judge time, says Sahani.
Bug to spider: I will control your offspring’s sex FAMED for their ruthless reproductive strategies, female spiders are in fact mere puppets in the hands of a parasitic bug that kills off their embryonic sons. Wolbachia bacteria infect up to two-thirds of insect species. They are transmitted through eggs, and so need their host to have as many females as possible. As a result, the bacteria have evolved a bag of dirty tricks to maximise their chances of making it to the next generation. The parasite can drive their hosts to virgin births, which result
in females only, gender-bend lads into ladies or simply kill males early in development. But until now nobody knew if Wolbachia could wreak havoc on spiders too. Bram Vanthournout at Ghent University in Belgium and colleagues have found that infected female dwarf spiders produce more females than those without Wolbachia. Giving the spiders antibiotics restored a normal sex ratio, proving that the previous female bias really was Wolbachia’s work (BMC
Evolutionary Biology, DOI: 10.1186/1471-2148-11-15). Because female-dominated clutches were smaller, the researchers suspect that the bugs kill off males long before birth. Vanthournout reckons that the bacteria may also be behind virgin births, which could even give spiders an evolutionary advantage. “Some social spiders need very few males, so male competition is high,” he says. Wolbachia might spare females the trouble of producing males who will never mate. George Grall/ngs/getty
Time stretches if you keep busy
Self-controlled kid, successful adult CHILDREN who lack self-control are more likely to become adults with poor health and finances. So say Avshalom Caspi at Duke University in North Carolina, Terrie Moffitt at King’s College London and colleagues, who followed the progress of 1000 children born between 1972 and 1973 in New Zealand. The team measured self-control by asking the children, as well as their parents and teachers, about their behaviour every two years between the ages of 3 and 15, and then at 18, 21, 26 and 32. Children with higher levels of self-control were more likely to have a higher socioeconomic background and a higher IQ. After adjusting for both factors, the team found that adults who had low self-control as children were more likely to be overweight, have substance abuse problems, gum disease and sexually transmitted infections. They were also less likely to be homeowners, and more likely to have been convicted of a criminal offence (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1010076108). The team suggests governments should employ policies to target self-control in children.
How the seahorse gained its shape IT IS easy to forget that the seahorse is a fish. With its equine head, pot belly and prehensile tail, it rivals the platypus in its peculiarity. But the seahorse’s form is not just for show: its arched neck acts like a spring that stores energy, ensuring it is ready to strike when it spots a meal. Biologist Sam Van Wassenbergh at the University of Antwerp, Belgium, and colleagues created mathematical models based on the body shape of seahorses and their straight-bodied cousins, pipefish. The models revealed that seahorses’ necks have the elasticity and stability
needed to let them lunge forward and grab a passing shrimp, even if it is some distance away. Pipefish, in contrast, cannot strike out so far and must settle for closer prey. This bend and snap technique is a vital hunting method for most seahorse species, as they are weak swimmers (Nature Communications, DOI: 10.1038/ncomms1168). “Like everyone, I have always wondered why seahorses look so bizarre,” says Adam Jones at Texas A&M University in College Station. “This is the first step in establishing it’s an adaptation.”
29 January 2011 | NewScientist | 15