The visual response of the purple shore crab, Hemigrapsus nudus, to ionizing and non-ionizing radiation Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5t34sn29j

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  • Bioelectric responses from the isolated eye of the purple shore crab were measured by the electroretinogram with stimulation by light from wavelengths of 250 to 800 nm, strontium-yttrium-90 beta radiation, 17.5 keV x-radiation, and 3-cm microwaves. Peak sensitivities to light stimulation were found at 350 and 500 nm. These peaks could be attributable to both the light absorption characteristics of rhodopsin, and fluorescence of eye structures by ultraviolet light. Responses were elicited only with rapid changes in stimulus intensity. Responses to beta radiation exhibited a peak at the onset of exposure, but no peak at the cessation. Responses to series of stimuli exhibited a decrease in amplitude with each succeeding stimulus, similar to that of visible light. Electroretinographic peaks did not decline to the baseline before the next response commenced. The results were considered to be due to direct stimulation of the photopigment and secondary stimulation produced by visible fluorescence and possibly Cerenkov radiation. The threshold absorbed dose was near 0.9 mrads. X-irradiation produced responses similar to those of visible light in that peaks were observed at the beginning and end of stimulation. No peaks were recorded with a gradual change in stimulus intensity. Such responses were thought to be from both direct photopigment stimulation and fluorescence. The x-ray threshold absorbed dose was approximately 50 mrads. Microwave irradiation resulted in neither direct visual stimulation nor modification of visible light responses during microwave exposure. Due to the low photon energy of this radiation, a direct influence on the photoreceptor mechanism was unlikely, although at much higher stimulus intensities, an interaction between the microwave electric field and nerve membranes might have been possible.
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