New Scientist - 21.09.2019

16 | New Scientist | 21 September 2019

Animal behaviour

Bones fire up body’s

response to danger

YOUR skeleton secretes a hormone

that helps to coordinate the flight-

or-fight response, suggesting this

part of our body is far from inert.

When faced with a sudden

threat, our heart and breathing

rate, blood pressure, circulating

blood sugar and body temperature

increase to prepare our muscles

for action. This response is known

to be controlled by nerve pathways

from the brain and hormones

Watery alien world

best bet yet for life

A PLANET twice Earth’s size with

water in its atmosphere has been

spotted 110 light years away. It may

be the best place found so far to

seek life beyond our solar system.

Björn Benneke at the University

of Montreal in Canada and his

colleagues used the Hubble space

telescope to observe the alien

world, called K2-18 b, as it passed

in front of its star. This is the first

time the atmosphere of a planet

of this size has been characterised.

Benneke’s team and another led

by Angelos Tsiaras at University

College London looked at the

edges of the planet as it transited

its star so that light shone through

the atmosphere, allowing them

to analyse what it was made of.

They found distinct signs of water

vapour. K2-18 b is also in the

habitable zone around its star,

defined as the area where a planet

could maintain liquid water on its

Exoplanets^ Physiology

GHOST crabs can “growl” by

grinding the teeth inside their

stomach. While many crustaceans

have such teeth to aid digestion,

the ghost crab is the first that

has been shown to use them

to communicate as well.

It has long been known that ghost

crabs (pictured) use noise to deter

intruders by flexing their claws,

making ridges near the joint rub

against each other. But when an

animal gets too close, the crabs hold

their claws upright, which prevents

them making these sounds.

Jennifer Taylor at the Scripps

Institution of Oceanography in

California noticed that even in

this position, the crabs still make

a rasping sound when threatened.

She and her colleagues couldn’t tell

what was causing the noise, so they

used X-ray videos to see what was

happening inside the crabs as they

growled in response to various

threats. These revealed that the

rasping coincided with movements

of the teeth in the crabs’ foreguts,

known as gastric mills, and that the

teeth weren’t grinding up food at

the time (Proceedings of the Royal

Society B, doi.org/dbgj).

Many animals, from worms and

molluscs to birds, have mechanisms

for grinding food in their gizzards

that can produce audible noises

(though birds swallow stones rather

than having internal teeth – as did

dinosaurs). Taylor suspects that

some of these animals also use

these noises for communication.

Some fish, such as grunts,

produce sounds using the teeth

in their throats. This is the closest

known equivalent to the ghost

crabs, says Taylor. Michael Le Page

Crabs unleash their inner

growl when intimidated

released by the adrenal glands.

Now, Gerard Karsenty at

Columbia University in New York

and his colleagues have discovered

that a hormone released by bones

called osteocalcin also has a role.

They found that blood levels of

osteocalcin quickly rose in people

when stressed. The same thing

happened in mice and rats (Cell

Metabolism, doi.org/dbgh).

The results build on the group’s

earlier work showing that bones

release osteocalcin to help muscles

burn fuel during exercise, and that

osteocalcin injections in older

mice make ageing muscles more

youthful. Together, these findings

suggest we need a radical rethink

of the role of bones, which have

previously been viewed as mostly

inert structures, says Karsenty.

The body may have different

ways of mounting a flight-or-fight

response so we have back-ups in

place in case one system fails, says

Robin McAllen at the University

of Melbourne in Australia.

Alice Klein

surface (Nature Astronomy,

doi.org/dbgp).

“This is the only planet that

we know of right now outside

our solar system that is in the

habitable zone, that has an

atmosphere and that has water

in it, which makes it the best

candidate for habitability

we know of,” said Tsiaras at

a press conference.

Planets like this one, between

the size of Earth and Neptune,

are common around other

stars, but their atmospheres

are difficult to study compared

with those of larger worlds.

While K2-18 b probably does

have a rocky core, it is likely to

be mostly gaseous, making it

more similar to Neptune than

Earth, says Laura Kreidberg at the

Harvard-Smithsonian Center for

Astrophysics in Massachusetts.

“The jury is still out on whether a

planet like this could be habitable.

If there were life there, it definitely

wouldn’t be like life as we know

it on Earth,” she says. Leah Crane

THEO ALLOFS/GETTY IMAGES

DOUGLAS SACHA/GETTY IMAGES

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