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This week THEY have a deadly bite, but a soft footfall. Tarantulas, it turns out, can spin silk with their feet. To crawl vertically and cling upside down, most spiders use minute claws and pads on their feet or “tarsi”. These work on rough surfaces, but may fail on smooth or dirty ones. While this is not a problem for small spiders that can survive long falls, for a heavy tarantula a slip could be fatal. To figure out how tarantulas make their way safely up vertical surfaces, Adam Summers of the University of California, Irvine, and colleagues analysed the footprints of Costa Rican zebra tarantulas (Aphonopelma seemanni) as they climbed a glass wall. This revealed that the spiders left fragments of sticky silk a few micrometres in diameter and up to 2.5 centimetres long. On looking closely at the spiders’ feet the researchers found microscopic spigots that resembled the creatures’ abdominal silk-producing spinnerets (Nature, vol 443, p 407). “With all the work that’s been done on spider feet it’s amazing to find something like this. Somehow it has been missed before,” says Summers. The discovery of these structures raises an interesting evolutionary question, as abdominal spinnerets are widely considered to be the remnants of ancient appendages. “It is thought that abdominal spinnerets could be vestigial legs,” says Todd Blackledge, who works on spider silk at the University of Akron in Ohio. The spinnerets have jointed segments and have been shown to move in sync with the legs when spiders walk. So far Summers and colleagues have found foot spigots only in tarantulas, so it is possible that they are a relatively recent adaptation to supplement the claws and pads. Identifying the genes involved in tarsal silk production will help determine whether they evolved to increase traction, or if they were co-opted from an organ with some other function. Testing these hypotheses will require detailed surveys of all spider species, says Summers, looking for any that might also have silken toes. Silky-footed tarantulas don’t come unstuck SOUNDBITES ‹ It’s obviously a legitimate question. Do you need to be a rocket scientist to be an astronaut?› NASA spokesman Robert Mirelson on the need for astronauts to have mechanical and construction skills as well as physics degrees (The New York Times, 24 September) ‹ We’ve got to get a greater understanding on this, on the frequency of fires, the earlier start to the season and if there’s any connection to climate change.› Kevin O’Loughlin of the Bushfire Cooperative Research Centre, on fears that after 10 years of below-average rainfall, Australia is on the brink of a catastrophic bushfire season (The Age, Melbourne, 25 September) ‹ We should be thinking in terms of a span of about five years. If public consensus developsit’s possible to do so earlier.› Japanese prime minister Shinzo Abe on how long it will take to revise his country’s pacifist constitution (The Korea Herald, Seoul, 25 September) It goes from career aspirations, to wondering whether I’m going to have a family, to trying to assure my future self that I’ve set aside enough money for retirement.Matt Sly on his futureme.org website, which allows you to send emails with time delays of anything from 30 days to 30 years (The Daily Telegraph, London, 25 September) ‹ They understood that they were selling death.› Attorney Michael Hausfeld applauds the ruling giving the go-ahead to a US lawsuit against big tobacco companies, accusing them of misleading smokers that “light” cigarettes are less harmful (BBC news online, 25 September) 12 | NewScientist | 30 September 2006 www.newscientist.com Surefooted, even on glassIMMORTALITY is dead, it was claimed last year, after bacteria were shown to get old and die. That obituary is now looking premature. Bacteria were long thought to enjoy a sort of immortality, because they simply divide symmetrically into identical daughter cells, neither of which is more likely to contain older components. This sets them apart from multicellular organisms, which contain non-reproductive cells that are doomed to age. Then last year, microbiologists in France found that Escherichia coli bacteria divide asymmetrically, with one daughter cell getting older components than the other. Over many generations, the “older” cells grow more slowly and eventually die (New Scientist, 5 February 2005, p 19). Now researchers led by Milind Watve of Abasaheb Garware College in Pune, India, have run a mathematical model that simulates the success of cells that develop either symmetrically or asymmetrically. This predicts that whether bacteria age or become immortal may depend on how well fed they are. Under good growth conditions with lots of nutrients, asymmetric division is favoured because the “old” cells die off but the “young” ones grow faster. When nutrients are scarce, however, symmetric cell division gives better survival and growth (Proceedings of the National Academy of Sciences, vol 103, p 14831). “Natural selection can favour symmetric division under certain conditions, so immortality is not dead,” says Watve. The idea could be tested by using fluorescent markers to discover how cell components are shared among daughter cells. “There’s every reason to believe this is real,” says geneticist Aubrey de Grey of the University of Cambridge. Rowan Hooper Bugs can live forever, but only if times are bad S. NIEDEREGGER MICHAEL REILLY “With all the work that’s been done on spider feet it’s amazing to find this. Somehow it has been missed before”

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This week–

THEY have a deadly bite, but a soft

footfall. Tarantulas, it turns out,

can spin silk with their feet.

To crawl vertically and cling

upside down, most spiders use

minute claws and pads on their

feet or “tarsi”. These work on rough

surfaces, but may fail on smooth

or dirty ones. While this is not a

problem for small spiders that can

survive long falls, for a heavy

tarantula a slip could be fatal.

To figure out how tarantulas

make their way safely up vertical

surfaces, Adam Summers of the

University of California, Irvine,

and colleagues analysed the

footprints of Costa Rican zebra

tarantulas (Aphonopelma

seemanni) as they climbed a glass

wall. This revealed that the spiders

left fragments of sticky silk a few

micrometres in diameter and up

to 2.5 centimetres long.

On looking closely at the

spiders’ feet the researchers

found microscopic spigots that

resembled the creatures’

abdominal silk-producing

spinnerets (Nature, vol 443,

p 407). “With all the work that’s

been done on spider feet it’s

amazing to find something like

this. Somehow it has been missed

before,” says Summers.

The discovery of these

structures raises an interesting

evolutionary question, as

abdominal spinnerets are widely

considered to be the remnants of

ancient appendages. “It is thought

that abdominal spinnerets could

be vestigial legs,” says Todd

Blackledge, who works on spider

silk at the University of Akron in

Ohio. The spinnerets have jointed

segments and have been shown to

move in sync with the legs when

spiders walk.

So far Summers and colleagues

have found foot spigots only in

tarantulas, so it is possible that

they are a relatively recent

adaptation to supplement the

claws and pads. Identifying the

genes involved in tarsal silk

production will help determine

whether they evolved to increase

traction, or if they were co-opted

from an organ with some other

function. Testing these

hypotheses will require detailed

surveys of all spider species, says

Summers, looking for any that

might also have silken toes. ●

Silky-footed tarantulas don’t come unstuck

SOUNDBITES

‹ It’s obviously a legitimate question. Do you need to be a rocket scientist to be an astronaut?›

NASA spokesman Robert Mirelson

on the need for astronauts to have

mechanical and construction skills as

well as physics degrees (The New York

Times, 24 September)

‹ We’ve got to get a greater understanding on this, on the frequency of fires, the earlier start to the season and if there’s any connection to climate change.›

Kevin O’Loughlin of the Bushfire

Cooperative Research Centre, on fears

that after 10 years of below-average

rainfall, Australia is on the brink of a

catastrophic bushfire season (The Age,

Melbourne, 25 September)

‹ We should be thinking in terms of a span of about five years. If public consensus develops…it’s possible to do so earlier.›

Japanese prime minister Shinzo Abe

on how long it will take to revise his

country’s pacifist constitution (The

Korea Herald, Seoul, 25 September)

‹ It goes from career aspirations, to wondering whether I’m going to have a family, to trying to assure my future self that I’ve set aside enough money for retirement.›

Matt Sly on his futureme.org website,

which allows you to send emails with

time delays of anything from 30 days to

30 years (The Daily Telegraph, London,

25 September)

‹ They understood that they were selling death.›

Attorney Michael Hausfeld applauds

the ruling giving the go-ahead to a US

lawsuit against big tobacco companies,

accusing them of misleading smokers

that “light” cigarettes are less harmful

(BBC news online, 25 September)

12 | NewScientist | 30 September 2006 www.newscientist.com

–Surefooted, even on glass–

IMMORTALITY is dead, it was claimed

last year, after bacteria were shown

to get old and die. That obituary is

now looking premature.

Bacteria were long thought to

enjoy a sort of immortality, because

they simply divide symmetrically into

identical daughter cells, neither of

which is more likely to contain older

components. This sets them apart

from multicellular organisms, which

contain non-reproductive cells that

are doomed to age. Then last year,

microbiologists in France found that

Escherichia coli bacteria divide

asymmetrically, with one daughter

cell getting older components than

the other. Over many generations,

the “older” cells grow more slowly

and eventually die (New Scientist, 5 February 2005, p 19).

Now researchers led by Milind

Watve of Abasaheb Garware College

in Pune, India, have run a

mathematical model that simulates

the success of cells that develop

either symmetrically or

asymmetrically. This predicts that

whether bacteria age or become

immortal may depend on how well

fed they are. Under good growth

conditions with lots of nutrients,

asymmetric division is favoured

because the “old” cells die off but

the “young” ones grow faster. When

nutrients are scarce, however,

symmetric cell division gives better

survival and growth (Proceedings of the National Academy of Sciences, vol 103, p 14831). “Natural selection

can favour symmetric division under

certain conditions, so immortality is

not dead,” says Watve.

The idea could be tested by using

fluorescent markers to discover how

cell components are shared among

daughter cells. “There’s every reason

to believe this is real,” says geneticist

Aubrey de Grey of the University of

Cambridge. Rowan Hooper ●

Bugs can live

forever, but only

if times are bad

S. N

IED

EREG

GER

MICHAEL REILLY

“With all the work that’s been

done on spider feet it’s amazing

to find this. Somehow it has

been missed before”

060930_N_p12.indd 12060930_N_p12.indd 12 25/9/06 5:38:14 pm25/9/06 5:38:14 pm