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frequentlyshowsadoublecrest(thekeel).Theloricaoftencoversthedorsalpart
ofthebodyonly,occasionallyextendingtoshieldtheentiretrunk,andsometimes
alsotheheadandfoot(Fig.2).Thecapsule-typeloricaisfoundinthegenera
Brachionus,Colurella,Lepadella,andTrichocerca.Atypicallytwo-platelorica
isshownbythegeneraLecaneandEuchlanis.Athree-plateloricaisobservedin
Metadiaschiza,theloricaofCephalodellaconsistingoffourorfiveplates.Still
morecomplexloricasoccurinMacrochaetusandTrichotria(Fig.2).
Rotifersarecharacteristicintheirmorphologicalvariability,forwhichreason
theyaredifficulttodescribe.Elasticityoftheirbodycoveraswellasthepresence
ofstrongtransverseandlongitudinalmusclesallowsthemtoretracttheheadand
foot,wherebythebodyresemblesasphere.Afterarotiferingestsalargeamount
offoodorwhenitcarriesnumerouseggsorembryos,thetrunkmayincreasein
volume.Foodexcessordeficiencygreatlyaffectsthesizeandshapeofrotifer
individuals(Fig.3).Characteristicvariationsinbodyshapearealsorelatedto
seasonalvariability(cyclomorphosis)(Fig.4).
Fig.3.Pleurotrochapetromyzon;A-regularform;B-starvedform;
C-satiatedform(afterWULFERT1969)
Thefluidfillingthebodycavityoccasionallycontainsnumerouslipiddrop-
letsandcellsthatfunctionasphagocytes:theyinterceptandstoreunnecessary
metabolicproducts.
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