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Theenergeticcostofrotiferswimmingisveryhigh,mostprobablybecause
ofthesmallbodysize.AsfoundbyEPPandLEWIS(1984),62%oftheentireme-
tabolismofBrachionusplicatilisisexpendedtowardslocomotion.
Feeding.Asalreadymentioned,therotiferfeedingmodeandthetypeoffood
ingesteddependonthestructureofboththeciliaryapparatusandthetrophi.
Mostplanktonicrotifersaresuspensionfeeders(Brachionus,Keratella);ben-
thicspeciesscrapfoodparticlesoffthesubstrate(Adineta,Lindia,Notommata);
epiphyticrotifersfeedonfoulingorganismssettledonaquaticplants(Euchlanis,
Philadinavus);predaciousspecieshuntandseizetheirprey(Dicranophorus);
somespeciespiercealgalfilamentstosuckoutthecytoplasmfromthecells
(Notommata).Sessilerotifersaresuspensionfeeders(e.g.,FlosculariaandPtygu-
ra)orpredators(Collotheca,Cupelopagis)(WALLACEandRICCI2002).
Rotifersfeedonverydiversefood:detritalparticles,bacteria,algae,protozo-
ansandotherrotifers.Theycanbeeitherpoly-ormonophagous.
Representativesoftwofamilies:theHabrotrochidaeandtheFiliniidaein-
gestexclusivelydetritusparticlesandbacteria,whilespeciesoftheEpiphanidae
andLindiidaefeedonlyonalgae(somespeciesareselectiveintheirchoiceof
algalspecies);asinglefamilyonly,theAsplanchnidae,isregardedastypically
predacious.
Phytophagousplanktonicrotifersfeedbasicallyonnanoplanktonicalgalspe-
ciesrepresentingallthealgaltaxa.
Somespecieswereobservedtobeselectivewithrespecttothesizeandqual-
ityoffoodparticlesingested.Ontheotherhand,numerousspeciesshowawide
spectrumoffoodparticlesizeandtype(POURRIOT1965,1977;DUmONT1977;
GILBERT1980a;WALLACEandRICCI2002).Forexample,POURRIOT(1965)found
theingestedparticlesizetodependontherotifersize:small(<600um)indi-
vidualsofCollothecaornatafedonalgaerepresentingthegeneraCryptomonas,
Phacus,Rhodomonas,andTrachelomonas,whilethoseindividualslargerthan
600umingestedPeridinium.GLIWICZ(1969,1974)observedplanktonicrotifers
topreferentiallyselectfoodparticleslargerthan1um:Keratellacochlearisin-
gestedparticlessmallerthan3um,keratellaquadratapreferredthosesmaller
than4um,andConochilussp.fedonthosesmallerthan6um.HILLBRICHT-IL-
KOWSKA(1972)foundKeratellacochlearistofeedonbacteriaandnanoplankton
cells1-2uminsize.
ExperimentalresearchdemonstratedBrachionusrubenstofeedpreferentially
onparticlesranginginsizewithin3-8pm,thedailyfoodrationrangingfrom3.6
thou.to16thou.algalcells/24h/individual;therelativefooduptakeoftheyoung-
estrotifersishigherby40-50%thantherelativeconsumptionofreproducing
females(PILARSKA1977a).
FoodpreferencesofAsplanchnapriodontaweredescribedbyEjSmONT-KARA-
BIN(1974).Thespeciesfeedsonotherrotifers:Keratellacochlearis,K.quadrata,
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