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WidelyknownforproducingbothmicticandamicticeggsareAsplanchna
girodi,A.priodonta,Conochiloidescoenobasis,andSinantherinasocialis.Mictic
andamicticfemalesaremorphologicallyidentical,buttheirlifehistoriesdiffer
(Fig.18A,B,C).Somepopulationscontaintheso-calledamphotericfemales
whichproducediploid,femaleeggsandhaploid,maleones.Instancesofpro-
ducingasexual(notfertilised)restingeggsareknowninKeratellahiemalis
(RUTTNER-KOLISKO1946)andSynchaetapectinata,theamicticdormanteggsof
thelatterbeingverydifferentfromthefertiliseddormanteggs(GILBERT1995).
Eggsofmostplanktonicspeciesareattachedtotheloricaortospecialfila-
mentsformedbythepedalglandsecretion.However,eggsofplanktonicspecies
areoftenlaidoncolony-formingalgae.Thisisparticularlyfrequentinthegenus
Trichocerca.Littoraland/orbenthicrotifersdonotcarrytheireggsbutlaythem
insteadonleavesofaquaticplantsorattachthemtovarioussubstrates.Thereare
alsoviviparousrotifers,e.g.,somespeciesofthegeneraAsplanchnaandConochi-
lus.Egg-layingincertainspeciesismorecomplexandprecededbyspecificbe-
haviours;forexample,Notommatacopeusshowsaprotectivebehaviourtowards
theeggslaidinacarefullychosenplace(CLémENTetal.1983).Averysimilar
behaviourwasreportedfromEuchlanisdilatatawherebytherotiferwasobserved
tobetouching,withitscorona,theeggslaidonasubstrate(WALSH1989).
Cleavageinrotifersiscomplete,non-uniform,sub-spiral,andstrictlydeter-
minate.Asearlyasattheblastomerestage,thereisonedistinctprogenitalcell
whichwillyieldreproductivecells.Theabilitytodividekaryokineticallytermi-
natesveryearly;consequently,thenumberofcellsmakinguptherotiferbodyis
low(usuallynothigherthan1000)andconstantinaspecies.Eventhenumberof
cellsofeachindividualorganisconstant;forexample,thenervoussystemconsists
of200-250cells.Theconstantnumberofcellsmakesregenerationimpossible.
Heterogony.Thephenomenonofheterogony(cyclicparthenogenesis)oc-
cursinrotifersbelongingtotheclassMonogonontaandinvolvesalternationof
mictic(sexual)andamictic(parthenogenetic)reproductioncycles.
Inthemicticcycle,amicticeggswith2nchromosomes,triggeredbyappro-
priatestimuli(e.g.,temperature,populationdensity,food),undergomeiosisto
hatchintomicticfemales(nchromosomes).Thosefemaleslayeggsoftwotypes:
1.theso-calledfemaleeggs(nchromosomes),and
2.theso-calledmaleeggs(nchromosomes).
Intheamicticcycle,adultfemaleslayamicticeggswith2nchromosomes;as
aresultofmitoticdivisions,thoseeggsgiverisetogenerationsofamicticfemales
with2nchromosomes.
The“female”eggshatchintohaploid,micticfemales(nchromosomes),
whilethe“male”eggsyield,withoutfertilisation,males(nchromosomes).Mitot-
icdivisionsinthemalesresultintheproductionofspermatozoawithnchromo-
someseach.Subsequently,themalesfertilisethemicticfemaleswhichinturnlay
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