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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4205

Donald L. Cronkite; Relations Between Photobehavior and Ionically Stimulated Swimming Behavior in Paramecium bursaria. J.Protozool. 33(1):52-55, 1986

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Cells of Paramecium bursaria, which harbor a symbiotic alga of the genus Chlorella, reverse the effective bear of their cilia and swim backward when stimulated in either of two ways. Ionic stimulation is introduction of cells into a solution high in K+ while step-down photostimulation is a sharp reduction in the intensity of light falling on the culture. Much is known about the mechanisms of ionic stimulation of ciliary reversal, but little is known about step-down photobehavior. Inhibitor of ionically stimulated ciliary reversal were applied to cells undergoing step-down photobehavior; Ca-channel inhibitors, neomycin and W-7, inhibit both behaviors. Activation of Ca-channels in the ciliary membrane is involved in step-down photobehavior, suggesting that the algae may alter the Paramecium membrane to make it more excitable.