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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 908

Matsuoka Tatsuomi; Negative phototaxis in Blepharisma japonicum. J.Protozool. 30(2):409-414, 1983

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The protozoan Blepharisma japonicum showed negative phototaxis caused by transient reversal of the direction of ciliary beat and changes of swimming velocity induced with varying intensities of light. The ciliary reversal occurred at 1-2 sec. after a sudden increase in light intensity. When light intensity was decreased, no response was observed. Moreover, the ciliates swam fast in light areas but slowly in dark areas; the mean velocity of swimming was 80 um/sec. at 5x10E2 lux but reached about 400 um sec at 5x10E3 lux. In addition, the cell body elongated in response to light application; the mean length of the body was 308 um at 5x10E2 lux, which increased to 397 um at 10E4 lux. Such body elongation seems to contribute to rapid swimming. Negative phototaxis may be an important behavior in B. japonicum because the organisms are killed by exposure to strong light.