The Week UK - 14.03.2020

NEWS 21

Dogsdon’tonlyusetheirnosestosmell.The

rhinarium (thecold, nerve-packed tip of the

nose) isan ultra-sensitive detector of heat –

potentially capable of sensing thepresence of

asmall mammaluptofivefeet away. For a

studynewly published on Nature Scientific

Reports,three dogs were trained to identify

which of two identicalobjects had been

heated to 12ºC aboveroomtemperature.

The thermalradiation given offwas so weak,

ahumanwouldhavetot ouchthe objectsto

tellthemapart, but the dogs correctly

identifiedthe warmerone, from fi ve feet

away, in double blindtest s.

The researchers ,fromSwedenand

Hungary, thenanalysedbrainscans of 13 awake dogsast heywere exposedto objects

emitting neutral or weak thermal radiation .The regio ninadog’sbrainthat connects

with its nose lit up when thedogs were exposed to the warmobjec t, but therewas

no reac tion when theywere exposedtothe neutralone.Black firebeetles,and some

snakes, are knowntohavethe ability to detectweak radi atingheat;but the only

other mammalknown tohave this“superpower” is the common vampirebat.

Health &Science

14 March 2020 THE WEEK

Thejellyfishthatfires“grenades”
DiversintheCaribbeanandtheGulfof
Mexicohavesometimesreportedfeeling
asifthewaterisstingingthem.Now,
scientistshavediscoveredwhy:Cassiopea
xamachana,ajellyfishcommontothose
seas,hasevolvedalethalextensiontoits
armoury–tinyballsofstingingcellsthat
itlaunches,grenade-style,atpotential
prey.Suspendedinstickymucus,theballs,
whichmeasurehalfamillimetreacross,
havehairsthatcausethemtowaft
throughthewater,boostingtheirchances
ofbumpingintoprey.Andtheycontain
enoughpoisontostunorevenkillsmall
fish–asresearchersatTohokuUniversity,
inJapan,discoveredwhentheyintroduced
brineshrimpintoatankcontainingthe
jellyfish.“Itwasareallyamazingmoment
whenwealltookturnslookingthrough
themicroscopeandsawthereweretiny
littlethingsmovingaboutinthemucus,”
leadauthorProfCherylAmestoldthe
NewScientist.Thestingingballs,dubbed
cassiosomes,killedthebrine shrimpin
underaminute, and thejellyfish then
used theirpulsatingmotiontosuckthem
towardstheirfeedingpores.Inthelab,
thecassios omessurvived forten days
aftertheirrelease, generatingenergy
fromspecks ofalgaethey contain.

Earthwas once covered in water
Threebillion yearsago,theEarthwasa
flooded“waterworld”withno emergent
continentsand just afewvolcanicislets
risingfromavastencirclingocean,
scientistshaveclaimed.Theteamatthe
University ofColorado Boulder,came
to thisconclusion afterstudyingarock
formationinthe northwestern Australian
outbackthat was onceaslabofocean
floor.By analysingoxygen isotopesinthe
3.2-billion-year-oldcrust, theydeduced

thatancientseawatercontainedsignificant

quantitiesofoxygen-1 8 –aslightly heavier

formofthegas thanthe oxygen-16which

predominates inseawatertoday. This,

theyclaim, provides strongevidence

thatcontinental land masseshadn’tyet

developed:if theyhad, oxygen-18would

not havebeen presentin such quantity

because clay-basedsoilswouldhave

absorbedmostofit.Thefinding,published

inNature Geoscience,couldhavean

impacton ourunderstandingof howlife

on Earth developed–addingweighttothe

theory thatitoriginatedin hydrothermal

vents inthe ocean, ratherthaninponds

on land, assomescientistsbelieve.

Thesecret of the XX chromosome

In countless mammal species, including

humans,females outlivemales,says The

Guardian.Inbirds,however,it tendsto

be the other way around.Now,scientists

fromthe UniversityofNewSouthWales,

Australia, have foundevidencethatthis

may bepartlydowntosex chromosomes.

Asiswellknown,female mammalshave

twoXchromosomes,whereasmaleshave

anXandaY.Inbirds,bycontrast,itis

the maleswhohavetherepeated

chromosome(ZZ; femaleshave ZW).In

fishandinsects,the pictureismoremixed,

but whenresearcherslookedat229 species

fromacrosstheentireanimal kingdom,

theyfoundaclearpattern: animalswith

two ofthesamesexchromosomeslived,

on average,17 .6%longerthanboththose

withasole sexchromosome and those

withtwodifferentones.Thefinding

bolsters one ofthemostcommon

explanationsforgreaterfemale longevity

in mammals:knownasthe“unguarded

Xhypothesis”, this holdsthathaving

two copiesoftheXsex chromosome

offersakindof geneticsafetynet,making

it easier forfemalestoavoidthe illeffects

of harmfulmutations.Ofcourse, there

aremanyotherfactorsaffectinglifespan.

In humans, malesmaybe morelikely to

indulge inrisky behaviour, forinstance.

Buttheresearchers suggestthat sex

chromosomes arean“underlying”one.

Fizzydrinks linked to strokes

Drinkingonesugaryfizzydrinkaday

in middleageappearstoput peopleat

significantly increased risk ofhavinga

heartattackorstroke. ATuftsUniversity

studyof 6,000Americansover40 found

thatthose who hadafizzy drinkaday

weretwiceaslikelyto havelow levelsof

the“good”cholesterol HDL(high-density

lipoprotein)thanthose whoavoidedthem;

theywerealso 53%morelikely tohave

raised levelsof triglyceride,a“bad”

cholesterolthatcanclogarteries.However,

no such associationwasfound among

thosewhodrankfruitjuiceand diet drinks.

Cassiopea xamachana: outsourcing stinging

Afteradecade of stagnation, life

expectancy in England appears to be

climbing again, reports The Guardian.

According to the ONS, life expectancy

for women at birth increased by four

months last year, rising to 83.6 years;

for men, it increased by three months,

to 79.9 years. Having increased steadily

throughout most of the 20th century,

life expectancy started to plateau in

the 2010s. This was widely blamed

on austerity cuts–and some have

suggested that the new figures show

that the easing of that programme is

already having an effect. However,

other experts, including former pensions

minister Steve Webb, pointed out that

one-off events, such asawarm summer,

can haveaskewing effect on the data.

“An improvement in life expectancy

data is very good news,” he said, but

“we should be wary of reading too

much intoasing le year’s figure s.”

Lifeexpectancyrising

Aheat-seeking sniffer

What the scientists are saying...

Dogs’ noses arecold to sense heat