Morphogenesis of Kiitricha marina Nozawa, 1941 (Ciliophora, Spirotrichea), a possible model for the ancestor of hypotrichs s. L.

Abstract

Recent studiessuggestedthatthemarineciliate Kiitricha Nozawa, 1941representsabasalbranchinthespirotrichs. The presentstudyreflectsthemorphogeneticalinvestigationof Kiitricha marina Nozawa,1941.Theresultslistedbelow show anextremelyunusualdevelopmentalpatterncomparedwithallotherknownformsintheclassSpirotricheaor hypotrichss.l. (i) Thedifferentiationoftheciliarystructuresfromtheprimordiaoccursaftercelldivision.Thismakes Kiitricha marina Nozawa,1941uniqueamonghypotrichss.l. (ii) Sincetheanlageoftheundulatingmembranesintheopisthederivesfromthedivisionofthededifferentiated parentalstructureandthusisnotformedindependently, Kiitrichamarina Nozawa,1941isalsouniqueamong spirotrichs. (iii) Mostsomaticcirralstructuresappearinapost-anlagepattern,i.e.allcirriexhibitaprimaryarrangementinthe sense thattheyaredistributedasthoughtheyhadjustbeensegregatedfromtheanlagen. (iv) Unlikemostotherknownhypotrichss.l.,theundulatingmembrane-anlagedoesnotcontributeafrontalcirrus. (v) Thedorsalkinetiesareformedintwoways:(a)fromtheposteriorportionofthecirralanlagenwhichlater generatethenewdorsalkinetysegments;and(b)bytheirregularproliferationofdikinetidsinthelongdorsal kineties. (vi) Allcirralanlagenareformedintrakinetallyfromthededifferentiatedparentalcirrianddevelopinaprimary mode. Takencollectively,thesefindingssuggestthat Kiitricha is abasalbranchinghypotrichandthereforea possiblemodelfortheancestorofthehypotrichss.l. & 2008 ElsevierGmbH.Allrightsreserved.