Regensburg 2013 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 20: Statistical Physics in Biological Systems II (joint with DY)
BP 20.2: Vortrag
Mittwoch, 13. März 2013, 15:30–15:45, H43
Retinal light collectors enhance underwater vision — •Moritz Kreysing1, Kristian Franze2, Mike Francke3, Andreas Reichenbach3, and Jochen Guck4 — 1Systems Biophysics, Department of Physics, LMU München, Germany — 2Department of Physiology, Development and Neuroscience, Cambridge University, UK — 3Paul Flechsig Institute, University of Leipzig, Germany — 4Biotechnology Center, TU Dresden, Germany
Vision at low light intensities relies on photoreceptors being able to detect individual photons. As an accepted rule, the light sensitive portions of vertebrate rods and cones, namely outer segments, increase in volume the darker the animals' habitat gets, in order to enhance the probability to capture incident photons. Consequently, the biggest outer segments are found in fish living in the deep sea. A peculiar exception to this rule are the eyes of some deep sea fish, as well as fish living in highly turbid rivers. In their retinas relatively short outer segments are bundled into spatially isolated groups, clearly not meant to maximize the probability of photon absorption. Based on a detailed morphological and optical study of multilayer light-collectors surrounding these segments [1], we argue that under extreme conditions in which quantum noise, i.e. the rate of spontaneous photo-pigment activation, becomes comparable to the rate of photon arrival, visual sensitivity cannot be achieved by large outer segments anymore. Instead the retinal focusing of light on very small receptors is the only way to lower the visual threshold further, or to see at near IR wavelengths. Reference: 1. M. Kreysing et al., Science 336(6089):1700-1703 (2012).