BBC Wildlife - UK (2020-08)

WILD AUGUST

Peopleona beachseldomrealise
there’sa carnivaloflifewithin
a stoneskimoftheshore.What
biologistsrefertoasthelower
intertidalzoneis onlyexposed
at theverylowest
tides,perhapsonce
ortwicea year,

andattractscreaturesyou’dthink

stayinmuchdeeperwater.At

varioustimes,thisbustlingworld

is visitedbymackerel,catsharks,

rays,flatfish,octopuses,lobsters,

seasquirtsandmuchelse

besides.Somearehereto

feed,otherstomateorlay

eggs,butspider

crabscometomoult.

Commonspider

crabsdwarfthe

greenish-brown

shorecrabsfamiliar

fromrockpools,

witha redbody

justabout

bigenoughtocovera dinner

plate,andspindlylegsthatspan

uptohalfa metre.Theirshell,

orcarapace,is protectedwitha

fringeofsharpspines,andoften

hostsgreenalgae,whichprovide

usefulcamouflage.Asinallcrabs,

theshellcan’texpand,somust

beshedasitsownergrows.But

sincethereplacementis softand

vulnerableat first,spidercrabs

migrateenmassetofavoured

moultinggrounds,wheretheycan

enjoysafetyinnumbers.Several

suchsitesareknowninsouth-west

England.Moundsofdiscarded

shellslittertheseabed,likethe

aftermathofa raucousparty.

FINDOUT MORE

Discover British marine life:

marlin.ac.uk

1 | SPIDER CRAB

Shell suits

THEONE

SHOW

Investigating moulting

shore crabs.

ONLINE