Animal behaviourZEBRA finches sing a special song to
their eggs when the weather is hot,
and this seems to program hatchling
cells to create less heat.
Zebra finches, which mostly live
in arid areas of Australia, sing “heat
calls” at temperatures above 26°C.
Previous studies have found that
the calls seem to reduce the growth
of offspring. A smaller body may
help young birds cope better in
higher temperatures.
Now, for the first time, we also
have evidence that when zebra
finch eggs are exposed to heat calls,
it changes how mitochondria –
energy-generating units inside
cells – work in hatchlings.
Mitochondria convert food
energy into a molecule called
adenosine trisphosphate (ATP),
which powers cells. They can also
use food energy to generate heat.To investigate, Mylene Mariette
at Deakin University in Geelong,
Australia, and her colleagues
kept zebra finch eggs at 37°C
for 10 days, before transferring
them into one of two incubators.
In one incubator, the researchers
played recordings of heat calls from
10am to 6pm every day until the
eggs hatched. In the other, they
played other zebra finch calls that
aren’t associated with heat.
At 13 days after hatching, the
researchers collected blood samples
from a total of 46 nestlings and
measured mitochondrial activity.
They found that mitochondria from
birds exposed to prenatal heat calls
produced more ATP relative to heat
production compared with offspring
that developed with control calls
(Proceedings of the Royal Society B,
doi.org/g8sf). Carissa WongParent birds sing a song of
mitochondrial manipulation
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News In brief
OLDER people who have cataract
surgery are less likely to develop
dementia afterwards.
The effect could be because
people who lose their eyesight
typically spend more time at
home, and so get less mental
stimulation – or it could be down
to a strange effect that cataracts
have on the colours that reach
the retina at the back of the eye.
Cataracts, which involve the lens
of the eye becoming cloudy with
age, are one of the most common
causes of vision loss in older
people. They are fixed by replacing
the lens with a plastic one.
Sight loss is a known risk factor
for Alzheimer’s disease and other
forms of dementia. So Cecilia Lee
at the University of Washington in
Seattle wondered whether cataract
surgery would have a correlation
with dementia incidence.
She and her colleagues tookHealthadvantage of an ongoing US study
that began in the 1990s to identify
risk factors for dementia. They
looked at the records of about
3000 participants who were 65 or
older and had either cataracts or
glaucoma, another eye condition
that is treated with surgery. This
was used as a comparison.
Over the next eight years, those
who had cataracts removed had,
on average, 71 per cent of the risk
of getting dementia as those who
had untreated cataracts. No such
differences showed up in people
with glaucoma (JAMA Internal
Medicine, doi.org/g8sq).
Cataract surgery could lower
the risk of dementia by enabling
“higher-quality sensory input
to the retina and therefore
improving stimuli to the brain”,
says Lee. Another idea is that as
cataracts filter out blue light, this
disrupts sensing by cells sensitive
to blue light that help govern our
body clock. Disturbing our
circadian rhythm has been linked
with dementia. Clare WilsonCataracts may be
linked to dementiaTWO stars with a combined mass at
least six times that of our sun that
are orbited by a gas giant make up
the largest planet-hosting star
system detected so far. The system
may challenge our currents ideas
of planetary formation.
Previous studies of planets in
close orbit to high-mass stars have
suggested that planets orbiting
stars of more than three times the
mass of the sun may be rare orSpaceeven non-existent. This is because
higher-mass stars emit larger
amounts of radiation, which
should cause the dense discs of
material like gas and dust around
such stars to evaporate before
they can coalesce into planets.
However, Markus Janson at
Stockholm University in Sweden
wondered whether giant planets
would still form around massive
stars as long as they orbited at
a great enough distance. Now,
Janson and his team have found
such a planet: a gas giant orbiting
a young binary star system called
b Centauri that is between six
and 10 times the mass of our sun.
The researchers first directly
imaged the system in March 2019
using the Very Large Telescope in
Chile and then conducted
follow-up observations in April- They found that the planet,
known as b Cen (AB)b, is 10.9 times
the mass of Jupiter and orbits the
two stars at 560 times the distance
between Earth and the sun
ES (Nature, doi.org/g8sj). Chen Ly
O/J
ANSON^ ET^ AL.‘Impossible’ planet
orbits binary stars18 | New Scientist | 18/25 December 2021