In brief–

with antiviral drugs such as

Tamiflu, says Cameron Simmons

at the Hospital for Tropical

Diseases in Ho Chi Minh City,

Vietnam, who led the study.

However, antibodies may be

costly and hard to mass-produce,

meaning their greatest benefit

may be treating the few people

who catch the disease directly

from birds, and to contain local

outbreaks. “This is not a tool for

public-health-level control of

H5N1,” says Simmons. The

antibodies may also not be

effective if the virus mutates.

H5N1 survived, compared with

none of the five mice not given

antibodies. They also worked as a

preventive therapy when given

before the mice were infected

(PLoS Medicine, DOI: 10.1371/

journal.pmed.0040178).

“If it works after three days,

that’s very good news,” says Albert

Osterhaus, a bird flu expert at

Erasmus University in Rotterdam,

the Netherlands, who was not

involved in the study. “It means

you could use it after the first

symptoms.” The antibody

treatment could be combined

PLANTS send out SOS signals

when they are under attack.

If insects are feeding on them,

some plants emit volatile

chemicals that attract enemies

of the insects. What is surprising,

though, is that neighbouring

plants not being eaten also send

out distress signals to call in

these “bodyguards”.

Why so-called secondary

signallers do it has been a mystery,

but now Yutaka Kobayashi and

Norio Yamamura of Kyoto

University, Japan, think they

have solved it.

The answer is family values,

or in evolutionary parlance, kin

selection. “My hypothesis views

secondary signallers as crying for

help to save their family,” says

Kobayashi. The pair used an

evolutionary model to show that

if the cost of making the SOS

signal was low and there was a

high likelihood of having relatives

growing nearby – both conditions

which are often true in real life –

then secondary signalling would

evolve (Evolutionary Ecology,

DOI: 10.1007/s10682-007-9165-9).

“Neighbouring undamaged

plants emit the secondary signal

probably to help the damaged

plants,” says Kobayashi.

Plants call guards

to protect family

BUYING a lady a drink to win her

favour is a trick not confined to men.

Some beetle females will mate simply

to quench their thirst.

The bean weevil Callosobruchus maculatus feeds on dry pulses. With

a diet like this, the male’s ejaculate is

a valuable water source for females.

Martin Edvardsson at Uppsala

University, Sweden, tested the idea

that females tap into this by keeping

them on dry beans with or without

access to water. Females living on

beans alone accepted more matings,

presumably to secure the water in the

seminal fluid (Animal Behaviour, DOI:

10.1016/j.anbehav.2006.07.018).

Edvardsson says that the energy

used to produce the ejaculate, which

makes up a whopping 10 per cent of

a male’s weight, is well spent. Once

impregnated, females lose interest in

sex – probably to avoid further injury

from the male’s spiny penis. They are

more likely to mate again if they are

thirsty. “This is a massive investment

for the male,” Edvardsson says. “It

buys them time before the females

remate and their sperm have to

compete with that of other males.”

Females with access to water lived

on average for a day and a half longer

than those without water. Since

average lifespan is only around nine

days, this makes quite a difference to

the total number of eggs they can lay.

ALTHOUGH they can only babble,

babies seem to have a keen eye for

speech: they can distinguish

between different languages simply

by reading your lips.

Whitney Weikum and colleagues

from the University of British

Columbia in Vancouver, Canada,

showed babies videos of talking

adults, with the sound turned off.

Babies soon got bored of the silent

clips, but they watched with

renewed interest when speakers

switched from English to French

(Science, vol 316, p 1159).

This ability lasted only until the

age of about 8 months – unless

the babies came from bilingual

households, when it continued. This

suggests that visual cues may help

babies avoid mixing up different

languages, says Weikum. “It supports

the idea that infants come prepared

to learn multiple languages and are

thus equipped to discriminate them

auditorily and visually,” she says.

Although there is no direct

evidence that visual cues help

children to learn a language, “it does

suggest that in language learning,

the brain may not be tied to speech

per se”, says Laura-Ann Petitto, a

language development researcher at

Dartmouth College in Hanover, New

Hampshire. She previously showed

that deaf babies use visual cues to

learn sign language, but “never did

we dream that young hearing babies

acquiring spoken languages also use

visual cues in this stunning way”.

AT FIRST the two Vietnamese

adults had nothing in common

but the good fortune to survive

a brush with H5N1 bird flu. Now

they share something else: their

immortalised blood cells may

help stop bird flu from becoming

a global pandemic.

Antibodies made from the

pair’s blood cells have cured

mice infected with the H5N1

virus, suggesting they might

make an effective treatment or

preventive therapy for humans.

All 20 mice given the antibodies

three days after infection with

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Blood of bird flu survivors gives promising antibodies

20 | NewScientist | 2 June 2007 www.newscientist.com

They’re watching your language

Female beetles have a thirst for sex

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