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Adler, K. K. (1976) Extraocular photoreception in amphibians. Photochemistry and Photobiology, 23 275–298. 
Added by: Sarina (15 Apr 2009 18:07:00 UTC)   
Resource type: Journal Article
DOI: 10.1111/j.1751-1097.1976.tb07250.x
BibTeX citation key: Adler1976
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Categories: Englisch = English
Keywords: Amphibien = Amphibians, Parietalorgan = Parietal Organ, Sehvermögen = Visual Perception
Creators: Adler
Collection: Photochemistry and Photobiology
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Abstract
Abstract—Amphibians possess extraocular photoreceptors (EOPs) which exclusively or together with the lateral eyes perceive light for various physiological and behavioral activities. Several kinds of EOPs are discussed but emphasis is given to the pineal complex: the dermal frontal organ (or stirnorgan) found only in frogs and toads among amphibians and the intracranial pineal body (or epiphysis cerebri) found in all Amphibia. Both structures are derived as dorsal evaginations of the diencephalon and have a retina-like fine structure. Both are sensitive to visible and UV light but not to IR, mechanical or chemical stimuli. The frontal organ gives chromatic and achromatic responses but in most species only achromatic ones are recorded from the pineal. Photopigments have been identified for some of these responses.

Pineal EOPs are involved in several activities: (i) neurosecretory activity by the subcommissural organ in the brain; (ii) body-lightening reaction in larval amphibians, involving the light-inhibited release by the pineal of a hormone, presumably melatonin, which contracts melanophores in the skin; (iii) cuing of circadian locomotor rhythms, including phase shifts and synchronization with environmental light cycles; (iv) perception of celestial cues for use in time-compensated compass orientation; and (v) possibly perception of linearly-polarized light.

Non-pineal EOPs have been implicated in (i) tail-darkening reaction of frog larvae where light has a direct effect on melanophores; and (ii) in phototaxis where unknown EOPs in various parts of the body and tail mediate withdrawal from light. Evidence for use of pineal and non-pineal EOPs and location of specific receptors is reviewed drawn from biochemical, ultrastructural, neurophysiological and behavioral studies. The possible use of EOPs for other biological functions and their possible adaptive value are briefly discussed.
Added by: Sarina  
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