Ref ID : 4235
Bland J. Finlay and Tom Fenchel; Photosensitivity in the Ciliated Protozoon Loxodes: Pigment Granules, Absorption and Action Spectra, Blue Light Perception, and Ecological Significance. J.Protozool. 33(4):534-542, 1986
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The ciliate Loxodes has a faint yellow-brown coloration due to large numbers of electron-dense granules located in the pellicle. Absorption and action spectra both indicate the presence of a blue-light receptor, which may be a flavin. Absorbance is minimal at wavelengths greater than 500 nm; there is a major peak at 360 nm and a pronounced shoulder at 435 nm. An action spectrum based on light-induced escape from oxic water shows a peak at 435 nm and a peak or shoulder at 360 nm. The pigment will generate superoxide when illuminated in the presence of oxygen. Loxodes living in an oxygen gradient in a spectrophotometer cell swims into and remains in anoxic water at light levels >/_10 Wm-2. Loxodes can be exposed to light levels of 2-20 Wm-2 in stratified lakes so its photobehavior can explain its periodic absence from oxic water. Photosensitivity in Loxodes may function as part of a predator-avoidance strategy.