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  • 1
    Electronic Resource
    Electronic Resource
    Effects of solar and ultraviolet radiation on motility, photomovement and pigmentation in filamentous, gliding cyanobacteria (1991)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 86 (1991), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of solar irradiation and artificial UV irradiation on several cyanobacteria (Anabaena variabilis and two strains of Phormidium uncinatum) have been studied. Both types of radiation affect the percentage of motile filaments and impair the linear velocity of the organisms. Long term exposure to UV radiation bleaches the photosynthetic pigments as determined by absorption difference spectra. Fluorescence excitation and emission spectra indicate that under ultraviolet radiation the energy transfer from the accessory pigments to chlorophyll is affected. Furthermore the structural integrity of the phycobilisomes seems to be impaired by continuous radiation and the photoreceptor pigments seem to be destroyed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1991.tb04805.x
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  • 2
    Electronic Resource
    Electronic Resource
    Phototaxis, gravitaxis and vertical migrations in the marine dinoflagellate Prorocentrum micans (1991)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 85 (1991), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The phototactic orientation of the marine dinoflagellate Prorocentrum micans was studied at three different ages and at several light intensities. High irradiances caused the cells to show negative phototaxis and low irradiances caused positive phototaxis. The precision of negative phototaxis reached a maximum in the early afternoon, while the precision of positive phototaxis was found to peak in the morning and at night. The cells also showed a pronounced negative gravitactic orientation, which had a maximum in precision in the early afternoon. The degree of gravitaxis was found to be constant over time when the cells were confined to a closed cuvette for up to 9 h. As a consequence of the orientation strategies, populations of Prorocentrum micans showed daily vertical migrations in a 3-m Plexiglas column. They accumulated in the top layers in the afternoon and were almost randomly distributed during the rest of the day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1991.tb04758.x
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  • 3
    Electronic Resource
    Electronic Resource
    Photoorientation in the freshwater dinoflagellate, Peridinium gatunense Nygaard (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 73 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The photoorientation of Peridinium gatunense, which causes massive algal blooms each year in Lake Kinneret (Israel), is characterized using a microcomputer-controlled video immage system. The cells show positive phototaxis under a wide light irradiance range from 1 lx up to about 18 klx, i.e., to about fifth of the natural solar radiation measured on the water surface. Above 20 klx diaphototactic movement of the cells is observed. The action spectrum of photoorientation based on fluence rate-response curves shows little activity below 520 nm and a peak of 640 nm. No obvious effect of photosynthetic inhibitors (DCMU and DBMIB) was found on phototaxis, although motility of the cells is drastically affected in the presence of high concentrations of these inhibitors. The results suggest that the photsynthetic mechanism is not involved in photoperception of phototactically active radiation. The ecological significance of photoorientation of the cells is discussed in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb03929.x
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  • 4
    Electronic Resource
    Electronic Resource
    Orientation of the green flagellate, Euglena gracilis, in a vertical column of water (1988)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 53 (1988), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The orientation of the green flagellate, Euglena gracilis, in a vertical column immersed in a pond was studied using automatic cell counting based on computerized image analysis. When exposed to solar radiation, the population moved downward in the column, probably guided by negative phototaxis, and formed a dense layer at the bottom. It is suggested that this behavior provides an opportunity for the organisms to escape from detrimental bright light. The downward movement is faster than the swimming speed of the cells allows and could be accelerated by a fluid mechanic effect. The upward movement observed at night may be due to the precise negative gravitaxis observed in the organisms. These antagonistic types of behavior allow the organisms to actively search for and to stay in areas with suitable conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1988.tb02660.x
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  • 5
    Electronic Resource
    Electronic Resource
    Multidirectional phototaxis by Dictyostelium discoideum amoebae (1985)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 29 (1985), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Phototaxis by solitary Dictyostelium discoideum amoebae is known to be complex, the amoebae turning either towards or away from the light, depending on conditions such as light intensity. Having previously shown that amoebal phototaxis can be bidirectional (2 preferred directions either side of the light source), we now report the discovery of multidirectional phototaxis by D. discoideum amoebae, with up to 12 different preferred directions. As in the bidirectional case, multidirectional phototaxis depends on direction-dependent transitions from turning away from to turning towards the light source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1985.tb00832.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of artificial and solar UV-B radiation on the gravitactic orientation of the dinoflagellate, Peridinium gatunense (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 73 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of artificial and solar UV-B radiation on the gravitactic (formerly called geotactic) orientation of the freshwater dinoflagellate Peridinium gatunense were measured under artificial UV-B radiation and in a temperature-controlled growth chamber under solar radiation in Portugal. Circular histograms of gravitaxis show the impairement of orientation after UV irradiation. The degree of orientation, quantified using the Rayleigh test and top quadrant summation, decreased as the exposure time to the radiation prolonged. The effects of artifical UV-B radiation on orientation are stronger than those of solar radiation, probably because the radiation source emits higher fluence rates below 300 nm than found in solar radiation. After UV radiation, the gravitactic orientation under artificially increased acceleration at 2 g was drastically affected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb03957.x
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  • 7
    Electronic Resource
    Electronic Resource
    Genetic Differences in Immunomodulation, Behavior, and Stress-Induced Organ Lesions (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 741 (1994), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1994.tb39667.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of enhanced UV-B irradiation on the red coloured freshwater flagellate Euglena sanguinea (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 13 (1994), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Euglena sanguinea, a freshwater flagellate isolated from a pond in the Fränkische Schweiz, orients itself in its habitat exclusively by positive phototaxis, which leads the organisms to the surface where they form a neuston. The algae are coloured red, as they contain haematochrome, a mixture of carotenoids, the main component being astaxanthin diester. Absorption spectroscopy shows that astaxanthin diester accumulates in cells irradiated with artificial UV-B irradiation, which suggests that the carotenoid is a photoprotective pigment. 15% enhanced UV-B irradiation impairs photoorientation and motility and photobleaches chlorophyll a while the carotenoids are less affected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1994.tb00064.x
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of tropical solar radiation on the motility of filamentous cyanobacteria (1993)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 12 (1993), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of tropical solar radiation on the motility of the cyanobacteria Anabaena variabilis, Oscillatoria tenuis and two strains of Phormidium uncinatum were studied in Ghana (4.30°N). The percentages of motile filaments were drastically reduced by unfiltered solar radiation. Covering the organisms with various long pass or band pass filters (WG320, GG395 or UG5) revealed that the UV-B, UV-A and visible light components of the solar spectrum were all effective in impairing motility in these organisms. Only partial recovery was observed and only after short exposure times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1993.tb00026.x
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of solar radiation and solar radiation deprived of UV-B and total UV on photosynthetic oxygen production and pulse amplitude modulated fluorescence in the brown alga Padina pavonia (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 19 (1996), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: The effects of solar radiation on photosynthetic oxygen production and pulse amplitude modulated (PAM) fluorescence were measured in the marine brown macroalga Padina pavonia harvested from different depths from the Greek coast near Korinth. In fluence rate-response curves the light compensation point for photosynthetic oxygen production increased and the saturation level decreased with increasing exposure time to solar radiation. Cutting off the UV-B wavelength range (280–315 nm) from solar radiation reduced the inhibition of photosynthesis, and the organisms were less affected when all of the UV radiation was filtered out. Algae collected from 7 m depth were much more prone to photoinhibition than those harvested from rock pools exposed to unfiltered solar radiation. During continuous exposure to solar radiation, rock pool algae showed photoinhibition after longer periods of time than specimens from 7 m or from dark adapted habitats. When subjected to unfiltered solar radiation the ratio of the variable fluorescence to the maximal fluorescence 〈inlineGraphic alt="inline image" href="urn:x-wiley:01686496:FEM53:FEM_19_mu1" location="equation/FEM_19_mu1.gif"/〉 (Fv = Fm− Fo) rapidly declined with increasing exposure time. However, again algae from 7 m depth were more prone to photoinhibition than rock pool algae. The differences between the two ecological strains were less obvious when UV-B or total UV was removed from solar radiation. Only in the latter case a complete recovery was observed after 2 h while, when exposed to unifiltered sunlight, only the rock pool algae recovered completely within that time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1996.tb00198.x
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