New Scientist - USA (2021-02-13)

13 February 2021 | New Scientist | 21

Ecology

Biology Animal behaviour

DNA clues to recent

bird extinctions

North American birds that

went extinct last century,

including the passenger

pigeon (pictured), weren’t

in genetic decline, suggests

a DNA analysis of samples

from museum collections.

This adds to evidence that

humans were responsible

for their disappearance

(Proceedings of the Royal

Society B, doi.org/ftdk).

Bats use late-night

winds to soar high

By exploiting winds that

sweep up south-facing

slopes at night, European

free-tailed bats in Portugal

can reach altitudes of

1600 metres. Birds ride

the winds during the day,

but until now it was unclear

whether bats could do the

same at night (Current

Biology, doi.org/ftks).

Wine analysis backs

up idea of ‘terroir’

A chemical analysis

of Malbec wines from

Argentina shows that it

is possible to identify the

vineyard they came from

and the year they were

produced. This supports

the concept of “terroir”,

that the combination of

climate and wine-making

practices can give wines a

unique flavour (Scientific

Reports, doi.org/ftb7).

Fairy circles resilient

to climate change

THE most famous so-called fairy

circles are grass-ringed patches

of barren earth found in Namibia

and Australia. Their lesser-known

cousins – transient rings of grassy

plants found in Chinese salt

marshes – could help explain why

such patterns naturally form and

may indicate ecosystem resilience

to climate change.

Li-Xia Zhao at East China Normal

University and her team took

sediment and plant samples from

SPERM have one goal – to fertilise

an egg – and it seems that some

mouse sperm cells with a certain

genetic mutation may boost their

chances by sabotaging rivals.

Previous research has shown that

mice with two copies of a genetic

variant called the t haplotype are

more likely to be infertile. But a new

study by Bernhard Herrmann at the

Max Planck Institute for Molecular

Genetics in Berlin and his colleagues

suggests that males with one copy

of it make some t haplotype sperm

cells that are more motile than

those they make without it.

This variant is a “selfish” genetic

element, because it can increase its

likelihood of being passed on to

offspring to higher than the usual

odds of 50 per cent. Herrmann and

his team have figured out how these

sperm gain their advantage.

The sperm with one t haplotype

variant produce molecules that are

able to disturb other sperm. They

make it hard for the rival sperm cells

to interact with their environment,

blocking various cell signalling

molecules that normally provide

the sperm with a sense of direction

(PLoS Genetics, doi.org/ftj8).

Although the t haplotype

sperm cells were more motile, the

researchers didn’t test their ability

to fertilise an egg. Karina Shah

transient rings, up to 100 metres in

size, on salt marshes in Shanghai.

Compared with samples from the

edge of the rings, those from the

centre had higher concentrations

of sulphides, which can cause

plant death at high levels. The

centre samples also had less

available soil nitrogen, which

can limit plant growth.

These variations are caused by

the growth and decomposition of

the plants. The team’s computer

models show that both nutrient

depletion and rising sulphide

levels would lead the vegetation

in the centre to die first, as that is

Spiders bag big prey

thanks to silk trick

SOME spiders take on animals that

are far larger than they are. To stop

such prey from running away, they

use their webs as pulleys to lift the

doomed animals off the ground.

Gabriele Greco and Nicola

Pugno at the University of Trento

in Italy watched five captive

specimens from the Theridiidae

family of common house spiders

catch cockroaches up to 50 times

more massive than themselves.

They found that the spiders

seemed to be using their body

weight to tension silk threads to

keep them taut before attaching

them to the roaches. The spiders

then continued to attach more

threads until their prey was lifted

into the air (Journal of the Royal

Society Interface, doi.org/ftkr).

“In the end, all these threads

create enough tension to lift the

prey, and that is when the spider

wins,” says Greco. The silk’s

strength is comparable with steel,

but it is as elastic as the silk you

would use to make clothes.

The behaviour is interesting

because you might not expect

such a relatively simple animal

to know how to catch its prey in

such a sophisticated way, says

Greco. It may allow spiders to

have an outsized impact on

their ecosystems. LC

where the plant has been growing

for the longest, leaving living rings.

These strange patterns of

grass aren’t just interesting to

look at – they indicate that their

environment can bounce back

from disruption more easily than

others. The researchers’ models

show that ecosystems with

transient rings recover from

disruptions like environmental

stress – a lack of oxygen in the

sediment, for example – to their

previous state twice as quickly as

those with persistent ring patterns

(Science Advances, DOI: 10.1126/

sciadv.abe1100). Bethan Ackerley

Some sperm can sabotage

rivals in the race to an egg

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Really brief

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