NEWS107
9
mall but highly effective hermit
crabs
Anyonewhohascollectedseashellson the
beachwhile onholiday andheld them in
the hollow of his hand, will undoubtedly
have receivedquitea shockat some stage
when a shell suddenly sprouted little legs
and tried to force itsway to freedom.InEu-
ropeanholidayareas the legswillgenerally
belong tomembers of thegenus
Clibana-
rius
,whichgrowno larger thana centime-
ter or two long. In the marine aquarium
these small hermit crabs areveryentertai-
ning, easy to keep, anduseful little creatu-
res,as theyareconstantlyon thesearch for
food andhence keep the tank freeof wa-
stes,whileat the same timenever causing
anyharm toother residents.
Australianhermit crab,
Calcinuselegans
.
All photos:FrankSchäfer
S
There isnodoubt that themain reason for settingupamarineaquarium is
the legendarycolorfulnessofthe fishesandcorals.Butoncethetank issetup
andmatured itbecomesclear thata fewextra littlehelpersmaybe required,
forexample tokeepdown thealgae,the
Aiptasia
,or thebristleworms,to loo-
sen thesubstrateabit,or tocleanupuneaten food.In thesea there isacrea-
turedesigned todealwitheverysuchproblemandsomeof themare, inad-
dition,sodelightful that it isworth takingacloser lookat them........
Asuseful as lovely
byLevinLocke
Anotherhermit crab species is
Calcinusele-
gans,
whichmaybeconsiderably largerata
good five centimeters in length,but is just
as harmless and beneficial.Moreover this
hermitcrab isarealbeauty!
Calcinuselegans
i
s importedmainly fromAustralia and two
points are particularly worth bearing in
mindwhen keeping it in thehome. Firstly
the species may be omnivorous, but the
focus of its diet is noticeably in the areaof
algae.Hence you shouldn't try to cultivate
algae in the
Calcinus
tank as any such at-
temptmaybecounteractedby
Calcinusele-
gans
.Sometimes even
Caulerpa
will be re-
gularlydecimated.And secondly,
C.elegans
grows rather quickly, andbecause its shell
doesn'tgrowaswell,thehermitwillneedto
"movehouse"regularly.Inordertoenable it
todo so, theaquaristmust provideagood
selectionof empty shellsof various sizes in
the tank.But that is the limitof thedifficul-
ties indealingwith theseprettycrabs.They
canevenbebred intheaquarium,although
the free-swimming larval stages usually
have tobe transferred tospecial tanks,as in
"normal" aquaria theyeither endup in the
filteror are regardedasawelcome supple-
mentary foodbyother tank residents.The
sexescannotbedetermined in livingspeci-
mens fromthepartsthatprotrude fromthe
shell,but if thehermit iswanderingaround
shell-less (egafteramolt) then the females
canbe recognizedby thepleopodson the
posterior body, as these limbs are comple-
telyabsent inmales.
Square-practical-good
Coral-reefaquaristsareusuallyaswaryofcrabs
astheDevilofholywater.Andnormally justifi-
ablyso,ascrabsarealmostinvariablyomnivor-
ous,whichshouldbe taken literally,aseating
everything.Eventhoughtheydon'tfindsome
livestockpalatable,thecrabswillkeeponchek-
kingtoseeifthetastehaschanged,andsooner
or later thecoralsstopopeningand fishes fall
preytothecrabsovernightwhentheyareslee-
ping (the fishes,not thecrabs,orelse itmight
betheotherwayround!).Inspecialaquaria,ho-
wever,crabsarenicepetsand interesting to
keep,but that isanotherstory.There is,howe-
ver,anotableexception to the ruleof "avoid
crabs in the reef aquarium":
Perconplanissi-
Seawater
