September 2020 BBC Wildlife 17WILD SEPTEMBER
teeth, starts to grind away at
a specific spot on the victim’s
shell. Since these teeth are made
from the same materials as
the shell that the snail is trying
to grind through, this process
needs chemical assistance. It
is provided by glands on the
underside of the foot and by an
accessory boring organ, which
lubricates the grinding surface
with a cocktail of hydrochloric
acid and enzymes.Perseverance pays
This double action takes time.
Grinding through the shells of
thicker bivalve molluscs can
take a couple of days. Once the
moon snail has broken through
the physical barrier, digestive
fluids are dribbled into the
cavity. The clam is turned to
chowder inside its own house.
A question remains. Why go
to all that effort, when other
shell-boring, predatory molluscs
can do a much quicker job by
nibbling through the thinner
parts of the shell? Perhaps it’s a
way of masking and controlling
the scene. If you open up a
shell, you also invite in the
competition – crabs and
shrimps may steal the meal.
This way, the moon snail has
everythingtoitself.Iustrat
ons
by
Peter
Dav
dScott/The
Art
Agency
NICK BAKER
is a naturalist, author and TV presenter.Revealsafascinating
worldofwildlifethat
weo enoverlook.samestrandlineasitsdinner
discards.Smooth,rounded,
shiny,almostpink...it looks
pretty‘cute’.Decoratedwith
bandsandwigglychevrons of
slightlydarkerpigment, it is
almosta caricatureofa snail,
somethingDisneyhimself
mighthavedrawn.
Whenalive,themoon snail
looks,atfirstsight,like a
snailridinga palepink magic
carpet.Thisis itsfoot,which
partlywrapsaroundthe
shell,smoothingout
anyresistancewhen
burrowingthrough
sandandsediment.
It alsoforms a skirt-
likeblanketas the
animalslinks over
thesurface.
Thesnaildetects waste
products wafted into the
water and wet sand by its prey.
It follows the scent plume to
its victim, then envelops the
hapless mollusc, whose only
defence is a shell. But even
with this calcium-carbonate
fortress clamped shut, the
moon snail is not deterred.
It now applies the dagger
hidden beneath its lubricious,
fleshy cloak, in the form of a
proboscis-like protuberance.
So, the physical onslaught
begins. The snail’s radula, an
organ equipped with multipleV
isitinga sandybeach
atthistimeofyear,
youmayliketoreflect
onsomethingthat
mightbegoingonbelowyour
feet.Lurkingbehindtheveil
ofwetsand,a killeris onthe
prowl.A driller-killer,noless.
You’llknowit is there,
becausecombingthestrandline
often delivers a pocketful of
cockles and other clam shells
with a neat hole close to where
the hinge would have been,
in a thickened region of the
shell called the umbo. The hole
is a precision job – rounded,
smooth and chamfered, with
the size (up to 3mm) relating to
that of the perpetrator.
The story surrounding this
hole – a feature much loved by
children, as it enables the shells
to be easily strung together in a
necklace – is a rather dark one.
Through this tiny, most perfect
of perforations, the shell’s
rightful resident was paralysed,
killed, liquidised and supped
up. And the animal that did
this dastardly deed? It’s called
the moon snail, Euspira catena,
and it looks about as innocuous
as a snail can possibly be.
Sometimes you’ll find a
moon snail’s shell on theNICK
BAKER
N
Hidden
NAME CALLING
What’s behind this snail’s alias?
The moon snail goes by various
other cryptic names, one being
necklace shell. It is tempting
to think this is because
the species’ feeding
process gifts
beachcombers
a by-product
complete with
thread-ready
holes. However,
the equally likelyexplanation is the moon snail’s
egg case. This ribbon-like
matrix of sand, mucous and
eggs forms a sti arc of a
structure. Sometimes
found washed up
on beaches in
late spring and
early summer, it
resembles the open
circlet of a torque-
style necklace.Estimates suggest 70
per cent of the dining
experience for the
moon snail is in the
preparations.D I D Y O U
KNOW?MOON SNAIL
Moon snails aren’t
deterred by a
mollusc’s shell.