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Happy days make you smarter
in Brief
For new stories every day, visit newscientist.com/news
Mystery of insects Poison cannibal toads with their own eggicide that roar like lions HOISTED by their own petard? In 2010, Rick Shine from the This suggests that the caught
Nigel Cattlin/Alamy
18 | NewScientist | 5 September 2015
Cane toad tadpoles produce chemicals that kill eggs of their own species, and that could give us a new way to clear the toad pest from Australia’s ponds. The toads have colonised all of north-eastern Australia since their introduction in the 1930s to help control an insect pest. Since then they’ve cut a swathe through predators – including crocodiles and marsupials – that eat them and die from their hallucinogenic poison, even causing local extinctions.
University of Sydney in Australia showed that toad tadpoles eat eggs of their own species. Traps baited with eggs were set to catch tadpoles so they could be removed. Now Shine has shown that tadpoles don’t just eat eggs, but also make a chemical that kills them – presumably to reduce competition. In the lab, 95 per cent of eggs died when placed in water containing other tadpoles (Journal of Applied Ecology, doi. org/635).
tadpoles should be left in the water so their secretions continue to kill nearby eggs. The next step is to conduct field trials, says Shine. He also wants to work out what the chemical is, and see if it can be used directly. “If the collateral impacts are minimal, and we’d have to check that carefully, we could potentially deploy it prior to the toad breeding season,” he says. “If we can construct a slow-release form, it could be a powerful weapon against the toad.” Henrik Weis/cultura/plainpicture
THEY are rather tiny to be kings of the jungle. Two species of mirid bug make sounds similar to the roars of big cats. Calls like these have never been detected before among insects, and we’re not sure how the bugs make them. The roars are too weak for our ears to pick them up, but they do cause minute vibrations in leaves where the bugs live. Valerio Mazzoni of the Edmund Mach Foundation in San Michele all’Adige, Italy, and his team exploited that to make them audible using a laser vibrometer, which detects and amplifies the leaf vibrations. “When you listen to these sounds through headphones, you’d think you were next to a tiger or lion,” says Mazzoni. If two males were put on the same leaf, a competitive roaring duet would follow. When one insect heard the other roar, it always followed suit. This suggests that, as in big cats, the calls might serve to establish dominance or attract females. Female mirids do not roar (Journal of Insect Behavior, doi. org/65h). Curiously, mirid bugs only roar while walking. And unlike crickets, they make their calls without visibly vibrating or rubbing any part of their body. “It must be a specific organ in the abdomen producing the roars,” Mazzoni says. He has yet to find anything that fits the bill.
Happy days make you smarter CHEER up, it might make you cleverer. We all have days when our brain goes at a snail’s pace, and IQ really does fluctuate. If we’re healthy, what’s going on? Sophie von Stumm at Goldsmiths, University of London, wondered if mood could be the brain’s dimmer switch. “On bad mood days, we tend to feel that our brains are lame and work is particularly challenging,” she said. “But scientists still don’t really know if our brains work better when we are happy.” Over five days, her team asked 98 volunteers to assess their mood and tested their short-term memory, working memory and processing speed. Bad mood didn’t correlate with worse cognitive performance. But when people reported feeling positive, von Stumm saw a modest boost in their processing speed. It could be that the impact of a bad mood failed to show up because its effects are only seen at the extremes – a minor funk may not be sufficient, she says. Her team have just launched an app called moo-Q to test the links between mood and IQ outside the lab, which more than 11,000 people have downloaded so far.
She ain’t heavy, she’s my sister EVER argued with your little sister? Now you can blame her for your weight problems too. Birth order is linked to a variety of outcomes later in life – firstborn kids are often taller and have a higher IQ, for example. But they are also more allergy-prone and now, it seems, fatter. A study of more than 13,000 pairs of sisters in Sweden found that although eldest girls are born slightly lighter than their younger sisters, they are about 30 per cent more likely to be overweight by their mid-twenties (Journal of Epidemiology and Community
Health, doi.org/65j). The findings back up earlier work in men. Co-author Wayne Cutfield from the University of Auckland, New Zealand, thinks the effect could be down to a first-time mum’s inexperienced uterus. Blood vessels that nourish the fetus seem to be slightly thinner in first pregnancies, causing firstborns to be lighter and then overcompensate by eating more. Gary Sacks of Deakin University in Melbourne, Australia, suspects social factors too. Maybe firstborns compete harder for food or get more money spent on them, he says.
For new stories every day, visit newscientist.com/news
Mystery of insects Poison cannibal toads with their own eggicide that roar like lions HOISTED by their own petard? In 2010, Rick Shine from the This suggests that the caught
Nigel Cattlin/Alamy
18 | NewScientist | 5 September 2015
Cane toad tadpoles produce chemicals that kill eggs of their own species, and that could give us a new way to clear the toad pest from Australia’s ponds. The toads have colonised all of north-eastern Australia since their introduction in the 1930s to help control an insect pest. Since then they’ve cut a swathe through predators – including crocodiles and marsupials – that eat them and die from their hallucinogenic poison, even causing local extinctions.
University of Sydney in Australia showed that toad tadpoles eat eggs of their own species. Traps baited with eggs were set to catch tadpoles so they could be removed. Now Shine has shown that tadpoles don’t just eat eggs, but also make a chemical that kills them – presumably to reduce competition. In the lab, 95 per cent of eggs died when placed in water containing other tadpoles (Journal of Applied Ecology, doi. org/635).
tadpoles should be left in the water so their secretions continue to kill nearby eggs. The next step is to conduct field trials, says Shine. He also wants to work out what the chemical is, and see if it can be used directly. “If the collateral impacts are minimal, and we’d have to check that carefully, we could potentially deploy it prior to the toad breeding season,” he says. “If we can construct a slow-release form, it could be a powerful weapon against the toad.” Henrik Weis/cultura/plainpicture
THEY are rather tiny to be kings of the jungle. Two species of mirid bug make sounds similar to the roars of big cats. Calls like these have never been detected before among insects, and we’re not sure how the bugs make them. The roars are too weak for our ears to pick them up, but they do cause minute vibrations in leaves where the bugs live. Valerio Mazzoni of the Edmund Mach Foundation in San Michele all’Adige, Italy, and his team exploited that to make them audible using a laser vibrometer, which detects and amplifies the leaf vibrations. “When you listen to these sounds through headphones, you’d think you were next to a tiger or lion,” says Mazzoni. If two males were put on the same leaf, a competitive roaring duet would follow. When one insect heard the other roar, it always followed suit. This suggests that, as in big cats, the calls might serve to establish dominance or attract females. Female mirids do not roar (Journal of Insect Behavior, doi. org/65h). Curiously, mirid bugs only roar while walking. And unlike crickets, they make their calls without visibly vibrating or rubbing any part of their body. “It must be a specific organ in the abdomen producing the roars,” Mazzoni says. He has yet to find anything that fits the bill.
Happy days make you smarter CHEER up, it might make you cleverer. We all have days when our brain goes at a snail’s pace, and IQ really does fluctuate. If we’re healthy, what’s going on? Sophie von Stumm at Goldsmiths, University of London, wondered if mood could be the brain’s dimmer switch. “On bad mood days, we tend to feel that our brains are lame and work is particularly challenging,” she said. “But scientists still don’t really know if our brains work better when we are happy.” Over five days, her team asked 98 volunteers to assess their mood and tested their short-term memory, working memory and processing speed. Bad mood didn’t correlate with worse cognitive performance. But when people reported feeling positive, von Stumm saw a modest boost in their processing speed. It could be that the impact of a bad mood failed to show up because its effects are only seen at the extremes – a minor funk may not be sufficient, she says. Her team have just launched an app called moo-Q to test the links between mood and IQ outside the lab, which more than 11,000 people have downloaded so far.
She ain’t heavy, she’s my sister EVER argued with your little sister? Now you can blame her for your weight problems too. Birth order is linked to a variety of outcomes later in life – firstborn kids are often taller and have a higher IQ, for example. But they are also more allergy-prone and now, it seems, fatter. A study of more than 13,000 pairs of sisters in Sweden found that although eldest girls are born slightly lighter than their younger sisters, they are about 30 per cent more likely to be overweight by their mid-twenties (Journal of Epidemiology and Community
Health, doi.org/65j). The findings back up earlier work in men. Co-author Wayne Cutfield from the University of Auckland, New Zealand, thinks the effect could be down to a first-time mum’s inexperienced uterus. Blood vessels that nourish the fetus seem to be slightly thinner in first pregnancies, causing firstborns to be lighter and then overcompensate by eating more. Gary Sacks of Deakin University in Melbourne, Australia, suspects social factors too. Maybe firstborns compete harder for food or get more money spent on them, he says.