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ORIENTATION OF SWIMMING FLAGELLATES BY SIMULTANEOUSLY ACTING EXTERNAL FACTORS 1
Author(s) -
Kessler John O.,
Hill Nicholas A.,
Häder DonatP.
Publication year - 1992
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.1992.00816.x
Subject(s) - phototaxis , biology , euglena gracilis , chlamydomonas , biophysics , irradiance , botany , physics , optics , genetics , chloroplast , mutant , gene
The directionality of phototaxis combined with gravitaxis was investigated experimentally for populations of the swimming alga Euglena gracilis Klebs. Two irradiances were used: a “weak” irradiance to elicit positive phototaxis and a “strong” irradiance to elicit negative phototaxis. In addition, by changing the density of cells in the suspension, the number of collisions between cells was varied to determine the effects of these collisions on the distribution of swimming directions in both the absence and the presence of illumination. We found that positive phototaxis was associated with a broader distribution of swimming directions than was negative phototaxis. In the latter case, the effect of phototaxis dominated over that of gravitaxis. Experiments on another swimming alga, Chlamydomonas nivalis Wille, showed that collisions between cells degraded the directionality of gravitaxis.