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ECOLOGICAL CONSIDERATIONS OF DIATOM CELL MOTILITY. I. CHARACTERIZATION OF MOTILITY AND ADHESION IN FOUR DIATOM SPECIES 1
Author(s) -
Cohn Stanley A.,
Weitzell Roy E.
Publication year - 1996
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.0022-3646.1996.00928.x
Subject(s) - diatom , biology , nitzschia , motility , botany , phototaxis , adhesion , frustule , phytoplankton , ecology , physics , microbiology and biotechnology , quantum mechanics , nutrient
To better determine the ecological role of motility in pennate diatoms, we quantitatively characterized several motility and adhesion properties of four species of motile pennate diatoms (Craticula sp., Pinnularia sp., Nitzschia sp., and Stauroneis sp. ) isolated from the same freshwater pond. Using computer‐assisted video microscopy, we measured speed, size/shape, functional adhesion, path curvature, and light sensitivity for these species, each of which shows a distinctive set of motile behaviors. The average speeds of Stauroneis, Pinnularia, Nitzschia , and Craticula cells are 4.6, 5.3, 10.4, and 10.0 μm · s −1 , respectively. Craticula and Nitzschia cells move in a relatively straight path (<4 degrees rotation per 100 μm movement), Stauroneis exhibits minor rotation (about 7 degrees per 100 μm movement), and Pinnularia rotates considerably during movement (about 22 degrees per 100 μm moved). Functional adhesion (as measured by the release rate of attached cells from the underside of an inverted coverslip) shows a half time for cell release of approximately 50 min for Craticula , 192 min for Pinnularia , and >1 day for Nitzschia and Stauroneis. Direction reversal at light/dark boundaries, which appears to be the main contributor to diatom Phototaxis, is most responsive for Craticula, Pinnularia , and Nitzschia at wavelengths around 500 nm. Craticula and Nitzschia cells are the most sensitive in the photophobic response, with over 60% of these cells responding to a 30‐1x light/dark boundary at 500 nm, whereas Pinnularia cells are only moderately responsive at this irradiance, showing a maximal response of approximately 30% of cells at 450 nm. Stauroneis cells, in contrast, had a maximal photosensitive response at 700 nm, suggesting that this cell type may use a different response mechanism than the other three cell types. In addition, Craticula and Pinnularia show a net movement out of the light spot when illuminated at 650 nm, whereas Stauroneis shows a net movement out of the light spot when illuminated at 450 nm. Such quantitative characterizations of species‐specific responses to environmental stimuli should give us a firm foundation for future studies analyzing the behavior of interspecies diatom competition for limited light or nutrient resources.