ENVIRONMENT
048 HowIt Works http://www.howitworksdaily.com
A
s the soft, squishy, pink things you first
encounter when you’re playing outside
as a kid, worms appear extremely fragile.
With a soft outer skin and little protection, when
you first saw them bur y themselves out of sight
and into the ground you may have wondered
how they managed it. A nd how can they possibly
nav igate these depths without any eyes or ears?
When worms dig they are mov ing a stream of
soil. Consuming the loam as they roam, this soil
passes through their elongated bodies before
being excreted behind them in their wake.
Digesting organic matter and leaves as food, they
alsoreturnnutrientstothesoilastheytravel.
Ina worldofdarkness,theonlymethodthey
havetosur v ivethecontinuousthreatsofbird
beaks,hungr ymolesandotherpredatorsisto
feeltheirwaythrough.NervesintheirbodiesThese fleshy creatures perform an impressive physical feat
to wiggle their limbless bodies through the soil
How worms dig
Words by Ailsa HarveyWormsusuallystaya fewcentimetresbelowground,
butthisdependsonhowwaterloggedthegroundis©GettyWorm movement
Soil saviours
Worms benefit soil just by burrowing
through it, providing nutrients and
ensuring oxygen reaches deeper
underground. Travelling in all directions
through the ground, earthworms produce
poresandgapsinthesoil.Theseactas
ventilationandcreateaccessforboth
oxygenandwater.
Withdeepverticaltunnelsbeing
constructedinsoilplentifulwithworm
life,a naturaldrainagesystemis created.
Allowingforthequickescapeofwater
throughtheseburrowsensuresthat
waterhassomewheretogoandprevents
thelikelihoodofa damagingflashflood.
Thenourishingnutrientswormsrelease
intotheearthincludenitrogen,
phosphorus,potassiumandcalcium.
Theseareessentialforthehealthy
growthofcrops.Aswormspopulatethe
soil,theyspreada rangeofbacteriafrom
theirinsidesaswellasincreasingthe
volumeoffungiandmucus.Insomeareas,earthwormscontribute 28 percent
ofcarbonfoundinthesoil© Gettycan detect light and v ibrations as they
manoeuv re, and their bodies move in response.
We only get to see worms’ movements for a small
fraction of their lives on the odd occasion they
surface, so what magic are they working when
out of sight and in their element?Howwormshaveadapted
tonavigatebelowgroundDigging anatomy
Vibrationsensing
Dangeroftencomesfromabove.
Fora blindearthworm,feelingthe
sensitivevibrationsusingthese
nervescanhelpthemtonavigate
beneaththesoiltosaferareas.
Circularmuscles
Theseoutermusclesareresponsible
forinitiatingtheworm’smovement
throughtheearth,bycontrating.Innermuscles
Contractionsoftheouterbody
causetheselongitudinalmusclesto
lengthen.Stretchingandshrinkingin
timewiththesecontractions,the
worm’sheadis abletomovefurther
alongthesoilandthetailfollows.Hairygrips
Toensurethatthewormdoesn’tstretchin both
directionsatthesametime,movingnowhere,tiny
hairscalledsetaeattachtothesoil.Thesetakeit
in turnstogripthesoilfromthefrontandback.Muscularmouths
Worms’mouthsaresostrong
theycanusethemtopull
leavesintotheground.Intestinalbreakdown
Makingupovertwo-thirdsoftheworm’sbody,
theintestineis responsibleforbreakingdown
food.Leftoversoilandorganicmattercontinue
totraveldownthelengthofthewormandare
releasedin theformofcastings.Thiswaste
productis highin nutrientsandhelpsfertilise
thesoilbehindit asit moves.Streamlinedhead
Theheadis pointed,helpingthempush
throughsoil.Thisendoftheirbodyis also
slightlyfirmer,whichhelpstomovetheearth
asideastheypushthroughsmallcrevices.© ShutterstockWidth control
Using contractions, these circular
muscles cause the inner muscles to
move in opposition.Fixed volume
When a contraction occurs,
the fluid and inner contents of
the worm must move along.Rounded
head
Its head temporarily
stops moving while it
waits for the rest of its body
tomovealong the burrow.Pointed head
When the worm’s muscles cause
its body to push forwards, the head
becomes pointed as it stretches,
piercing through the earth.Anchor point
With each muscle segment working independently, the
thicker segments attach to the walls of the burrow. This
prevents backwards movement.© Shutterstock