Ref ID : 3769
Bodo Diehn, James R. Fonseca, and Theodore Louis Jahn; High Speed Cinemicrography of the Direct Photophobic Response of Euglena and the Mechanism of Negative Phototaxis. J.Protozool. 22(4):492-494, 1975
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The shock reaction of Euglena gracilis strain Z to a sudden increase in light intensity (the "direct photophobic response") was examined by high speed cinemicrography. The response is expressed as a turning reaction toward the dorsal side of the cell, after a transduction time of 0.1-0.5 sec after the onset of stimulation. Transduction times, turning rates, and flagellar beat frequencies were measured by analyzing the filmed sequences. The experimental data are consistent with a mechanism of directional homeostasis in negative phototaxis that is based upon shading of the photoreceptor by the cell's posterior end.