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Dead sons may explain killer whale menopause
Alex Wild
IN BRIEF Bees reboot brain genes to suit a task
Failed young queens must labour as lowly commoners PITY the queen that is demoted to the status of mere worker. That’s what happens to leafcutter ant queens that fail to leave and start a new colony, but it’s actually unusual – in most ant species failed queens are eaten by their sisters. Acromyrmex echinatior ants collect huge volumes of leaves and cultivate a special fungus on them. The ants eat the fungus and nothing else. Leafcutter colonies have several worker castes: the larger ones collect the leaves and the smaller ones tend the fungal gardens. Reproductive males and females leave the nest to start
new colonies, but Volker Nehring, a behavioural ecologist at the University of Freiburg in Germany, noticed that in A. echinatior would-be queens remained in the nest (Current Biology, doi.org/jcc). Nehring captured some newly hatched queens and removed their wings, preventing them from leaving on their mating flights. The grounded queens began behaving like workers, taking care of larvae and attacking ants from other colonies. The queens of other eusocial ants have lost the ability to behave like workers, so they can’t adapt. However, A.echinatior queens have retained their worker skills because they take an active role in setting up their own colonies. Nehring thinks they are safe from the other workers because leafcutter ants eat only fungus.
Killer whale menopause saves sons’ lives THEY may be one of the largest predators on the planet, but orca males are also mummy’s boys. A long-term study of wild killer whales shows that adult males are highly dependent on their mothers. The finding throws new light on why orcas are the only non-human animals – apart from pilot whales – known to go through an extended menopause. Female orcas live to be 90 but 14 | NewScientist | 22 September 2012
stop reproducing in their 30s. To understand why, Darren Croft of the University of Exeter, UK, analysed records of 589 orcas between 1974 and 2010, comparing the fates of adult animals with living and dead mothers. Having a living mother greatly increased an orca’s chances of survival, particularly for males over 30 (Science, DOI: 10.1126/ science.1224198). “There’s a 14-fold
increase in the risk that sons over 30 years old die in the year after their mothers die,” says Croft. Females were less affected. Orca females may go through the menopause to ensure the survival of their sons, who will then have more offspring carrying their genes. Male orcas breed with females in other pods, then return to their home pod. “That means the matriarchs are not paying costs of rearing their own sons’ children,” says Croft.
WORKER honeybees shuttling between foraging and nursing tasks switch groups of genes on and off in their brains for each job. Andrew Feinberg of Johns Hopkins University School of Medicine in Baltimore, Maryland, emptied a hive to trick forager bees into becoming nurse bees. To see what effect this had on their brains, he scanned their brain-cell DNA for evidence of epigenetic modification – the addition or removal of small “methyl” tags that switch groups of genes on and off. They found that each role had a specific and reversible pattern of gene activation. It’s the first time that reversible behaviour has been linked to epigenetic change, says Feinberg (Nature Neuroscience, doi.org/jc3). Several human disorders like addiction and schizophrenia have an epigenetic component, so understanding how this works could lead to new treatments.
The fall of a sungrazing comet IN DECEMBER 2011, a comet called Lovejoy ploughed into the sun’s corona – and to everyone’s surprise, emerged on the other side. But it turned out that Lovejoy couldn’t take the heat for long. Zdenek Sekanina and Paul Chodas of NASA’s Jet Propulsion Laboratory in Pasadena, California, reanalysed pictures taken on 20 December, showing that Lovejoy’s nucleus, the cometary equivalent of a head, had suddenly vanished. Based on the structure and composition of other comets, they concluded that the dusty core disintegrated about two days after its trip through the corona. They put it down to a build-up of thermal stress that continued to destroy it from within (The Astrophysical Journal, doi.org/jck).
IN BRIEF Bees reboot brain genes to suit a task
Failed young queens must labour as lowly commoners PITY the queen that is demoted to the status of mere worker. That’s what happens to leafcutter ant queens that fail to leave and start a new colony, but it’s actually unusual – in most ant species failed queens are eaten by their sisters. Acromyrmex echinatior ants collect huge volumes of leaves and cultivate a special fungus on them. The ants eat the fungus and nothing else. Leafcutter colonies have several worker castes: the larger ones collect the leaves and the smaller ones tend the fungal gardens. Reproductive males and females leave the nest to start
new colonies, but Volker Nehring, a behavioural ecologist at the University of Freiburg in Germany, noticed that in A. echinatior would-be queens remained in the nest (Current Biology, doi.org/jcc). Nehring captured some newly hatched queens and removed their wings, preventing them from leaving on their mating flights. The grounded queens began behaving like workers, taking care of larvae and attacking ants from other colonies. The queens of other eusocial ants have lost the ability to behave like workers, so they can’t adapt. However, A.echinatior queens have retained their worker skills because they take an active role in setting up their own colonies. Nehring thinks they are safe from the other workers because leafcutter ants eat only fungus.
Killer whale menopause saves sons’ lives THEY may be one of the largest predators on the planet, but orca males are also mummy’s boys. A long-term study of wild killer whales shows that adult males are highly dependent on their mothers. The finding throws new light on why orcas are the only non-human animals – apart from pilot whales – known to go through an extended menopause. Female orcas live to be 90 but 14 | NewScientist | 22 September 2012
stop reproducing in their 30s. To understand why, Darren Croft of the University of Exeter, UK, analysed records of 589 orcas between 1974 and 2010, comparing the fates of adult animals with living and dead mothers. Having a living mother greatly increased an orca’s chances of survival, particularly for males over 30 (Science, DOI: 10.1126/ science.1224198). “There’s a 14-fold
increase in the risk that sons over 30 years old die in the year after their mothers die,” says Croft. Females were less affected. Orca females may go through the menopause to ensure the survival of their sons, who will then have more offspring carrying their genes. Male orcas breed with females in other pods, then return to their home pod. “That means the matriarchs are not paying costs of rearing their own sons’ children,” says Croft.
WORKER honeybees shuttling between foraging and nursing tasks switch groups of genes on and off in their brains for each job. Andrew Feinberg of Johns Hopkins University School of Medicine in Baltimore, Maryland, emptied a hive to trick forager bees into becoming nurse bees. To see what effect this had on their brains, he scanned their brain-cell DNA for evidence of epigenetic modification – the addition or removal of small “methyl” tags that switch groups of genes on and off. They found that each role had a specific and reversible pattern of gene activation. It’s the first time that reversible behaviour has been linked to epigenetic change, says Feinberg (Nature Neuroscience, doi.org/jc3). Several human disorders like addiction and schizophrenia have an epigenetic component, so understanding how this works could lead to new treatments.
The fall of a sungrazing comet IN DECEMBER 2011, a comet called Lovejoy ploughed into the sun’s corona – and to everyone’s surprise, emerged on the other side. But it turned out that Lovejoy couldn’t take the heat for long. Zdenek Sekanina and Paul Chodas of NASA’s Jet Propulsion Laboratory in Pasadena, California, reanalysed pictures taken on 20 December, showing that Lovejoy’s nucleus, the cometary equivalent of a head, had suddenly vanished. Based on the structure and composition of other comets, they concluded that the dusty core disintegrated about two days after its trip through the corona. They put it down to a build-up of thermal stress that continued to destroy it from within (The Astrophysical Journal, doi.org/jck).