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Hagins Wa

Bio: Hagins Wa is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 21 citations.

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Journal ArticleDOI
TL;DR: By fitting the measurements to a model, it is found that coupling between drone retinulas is stronger than in the locust but weaker than in Limulus, and the degree of coupling accounts satisfactorily for the difference in input resistance between Apis and Locusta cells.

152 citations

Journal ArticleDOI
TL;DR: In this paper, the Schwarzschild law (a power law generalization of the reciprocity law) appears to model adequately photoresponse vs. radiant flux for most materials and systems.

151 citations

Book ChapterDOI
01 Jan 1972
TL;DR: Most of the knowledge of photoreception in the invertebrates has been derived from those species with a well developed visual apparatus, and in two phyla, conspicuous image-forming eyes have evolved.
Abstract: The invertebrates comprise a large and diverse array of animals. In lower forms responses to light are frequently marked but are mediated by relatively simple eyes (ocelli) or anatomically unspecialized receptors in the dermis or nervous system. In two phyla, however, conspicuous image-forming eyes have evolved. For obvious reasons, most of our knowledge of photoreception in the invertebrates has been derived from those species with a well developed visual apparatus.

90 citations

Journal ArticleDOI
TL;DR: These and previous results suggest that the two R1-6 spectral peaks are ultimately mediated by one rhodopsin, and calculations show electro-retinographic sensitivity to be extremely high, perhaps measurable at less than one absorbed quantum per rhabdomere.
Abstract: Low vitamin A rearing decreases sensitivity and eliminates the ultraviolet but not the blue sensitivity maximum in R1-6 inDrosophila, Calliphora andMusca (Figs. 2–4). Spectral adaptation functions for control and vitamin A deprived flies yielded derived stable metarhodopsin absorption spectra from spectral sensitivity. Metarhodopsin has a long wavelength maximum and also has an ultraviolet maximum especially in the normal vitamin A condition (Figs. 2–4). M-potentials (fast early-receptor-like potentials) were obtained (Fig. 1) from all three genera in normal vitamin A rearing and were used for spectral adaptation studies (Figs. 2–3); the latter data are approximate inverses of sensitivity based spectral adaptation data. Thus, sensitivity must reflect proportion of rhodopsin, with metarhodopsin being inert in receptor potential generation. Vitamin A effects on spectral functions were further investigated inDrosophila. Ultraviolet (370 nm) and visible (470 nm) sensitivities varied approximately linearly with dietary vitamin A dose (Fig. 5); 370 nm sensitivity decreased more than 470 nm sensitivity at lower doses. Increasing adaptation intensities of 370 and 470 nm caused parallel decreases in spectral sensitivity assayed at 370 and 470 nm in normal vitamin A flies (Fig. 6); the adapting intensities were sufficient to convert photopigment. These and previous results suggest that the two R1-6 spectral peaks are ultimately mediated by one rhodopsin. R1-6 rhabdomeres were structurally similar in high and low vitamin A flies but emitted a long wavelength fluorescence to ultraviolet excitation in high vitamin A flies only (Fig. 7). These results suggest some form of energy transfer; i.e., a carotenoid may capture ultraviolet quanta and transfer energy to rhodopsin via inductive resonance. Spectral adaptation data are consistent with a calculated high rhabdomeric optical density of ECL=0.26 (i.e., 45% of incident light is absorbed) derived from presently available data onDrosophila. Calculations show electro-retinographic sensitivity to be extremely high, perhaps measurable at less than one absorbed quantum per rhabdomere.

83 citations

Journal ArticleDOI
TL;DR: Measurements of isolated crayfish rhabdoms illuminated transversely show that their photosensitive absorption exhibits a dichroic ratio of 2 in situ, and the rhabdom's functional dichroism thus arises from its specific fine structural geometry.
Abstract: Microspectrophotometric measurements of isolated crayfish rhabdoms illuminated transversely show that their photosensitive absorption exhibits a dichroic ratio of 2 in situ. The major absorption axis matches the axial direction of the closely parallel microvilli comprising the receptor organelle. Since these microvilli are regularly oriented transversely in about 24 layers, with the axes of the microvilli at 90° in alternate layers, transverse illumination of a properly oriented rhabdom displays alternate dichroic and isotropic bands. Because all the microvilli from any one cell share the same orientation, the layers of microvilli constitute two sets of orthogonal polarization analyzers when illuminated along the normal visual axis. Furthermore, since the dichroic ratio is 2 and transverse absorption in isotropic bands is the same as that in the minor absorbing axis of dichroic bands, the simplest explanation of the analyzer action is that the absorbing dipoles of the chromophores, as in rod and cone outer segments, lie parallel to the membrane surface but are otherwise randomly oriented. The rhabdom's functional dichroism thus arises from its specific fine structural geometry.

76 citations