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Meissl, H. & Ueck, M. (1980) Extraocular photoreception of the pineal gland of the aquatic turtlePseudemys scripta elegans. Journal of Comparative Physiology A, 140 173–179. 
Added by: Sarina (02 Apr 2009 15:48:56 UTC)   
Resource type: Journal Article
DOI: 10.1007/BF00606309
BibTeX citation key: Meissl1980
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Categories: Englisch = English
Keywords: Parietalorgan = Parietal Organ, Schildkröten = Turtles, Sehvermögen = Visual Perception
Creators: Meissl, Ueck
Collection: Journal of Comparative Physiology A
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Acetylcholinesterase-positive nerve cells of the sensory type were demonstrated predominantly in the region of the pineal stalk and sporadically in the rostral part of the pineal organ ofPseudemys scripta elegans. In agreement with these findings successful extracellular electrical recordings were obtained from single nerve cells of the proximal region of the pineal stalk. The recorded cells showed a spontaneous discharge that was inhibited by light stimuli of all wavelengths from 400 to 750 nm. The action spectrum of the pineal cells investigated revealed a maximum between 606 and 650 nm, after correction was made for the selective filter effect of the blood sinus in front of the pineal gland. The absolute intensity threshold of the cells was at 0.07 lm/m2 in the exposed pineal organ.
Measurements of tissue absorbance in front of the pineal gland indicate that light of longer wavelengths (600–750 nm) penetrates most effectively. Approximately 2.0 log units were absorbed around 600 nm, where the pineal cells possess a maximum sensitivity, and about 5.0 log units at 450 nm. From these values an intensity threshold in the photopic range of 7–70 lm/m2 was calculated in the intact animal. Thus, despite the strong absorbance of the overlying tissue, the pineal gland is a very sensitive light dosimeter within the photopic range of luminances.
The authors are most grateful to Dr. B. Vivien-Roels for her aid in the early part of this study and to Prof. E. Dodt for many valuable suggestions and helpful criticism.
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