Calcium-induced ciliary reversal in the extracted models of "Pawn", a behavioral mutant of Paramecium.

"Pawn," a genic mutant of Paramecium aurelia, cannot swim backward as the wild type can upon proper stimulation. In contrast, after membrane disruption by Triton X-100, the adenosine triphosphate-magnesium reactivated models of Pawns swim backward in the presence of calcium as wild-type models do. Thus, the mutant phenotype is due to an impairment in the membrane and not in the calcium-sensitive motile system.