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Optical Mimicry and Communication in Cephalopods

http://symbiol.blogspot.com/. Optical Mimicry and Communication in Cephalopods. ENGN/BIOL 267, Fall 2013. Master of Camouflage. Where’s Waldo…err, the octopus?. Cuttlefish Camouflage. How does it do it?.

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Optical Mimicry and Communication in Cephalopods

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  1. http://symbiol.blogspot.com/ Optical Mimicry and Communication in Cephalopods ENGN/BIOL 267, Fall 2013

  2. Master of Camouflage

  3. Where’s Waldo…err, the octopus?

  4. Cuttlefish Camouflage

  5. How does it do it? • If you are an octopus (or squid, or whatever cephalopod), what “equipment” do you need to pull off the color changes? • Reflectors • Pigment + = http://www.toolsandleisure.co.uk/round-amber-self-adhesive-reflector-294-p.asp

  6. Chromatophores: Pigment Sacks Young et al, 2001 Mathger and Hanlon, 2007 • Variable size/radius • Under muscarinic control • Color spectrum somewhat limited

  7. Chromatophores in Action http://blog.backyardbrains.com/2012/08/insane-in-the-chromatophores/

  8. Iridophores: Reflectors * Stacks of protein plates (reflectins) in cytoplasm * They are, by themselves, colorless * Located beneath chromatophores Cytoplasm Protein plates 1um Cooper, 1990

  9. Iridophores are active *Spacing between layers can change. * Changing layer spacing implies changing reflected wavelength * Under neural and chemical control (Ach) Cytoplasm Protein plate Scale bars: 250 nm Cooper, 1990 Cooper, 1990 Mathger, 2007

  10. What is measured and how? To computer for data acq. and analysis--.e.g, the reflectance spectra! Photo Multiplier Tube: Collects light and amplifies Reflected from squid skin Light source with chromatic filter (and polarizer) Tissue prep: Thin slice of squid skin Choose color of incident light and measure input intensity Iinc Measure intensity of reflected light Iref, then compute: R = Iref/Iinc

  11. Two to Tango: Chromatophore-Iridophore Interaction Yellow chromatophore+ green iridophore = dark yellow Yellow chromatophore + red iridophore = orange!

  12. Biomimicry in Cephalopods: Part Deux 1um

  13. Application of Optics Convenient Physics model The Real Thing Cytoplasm Protein plate Scale bars: 250 nm

  14. Traveling Waves Frequency f How wave varies with time Wavenumber k = 2p/l How wave varies in space

  15. Different strokes for different folks • Wavelength changes depending on medium in which it is traveling • nolo= nili = nclc lI lc lo

  16. Wavelength changes depending on material/medium iridophore cytoplasm air

  17. Cytoplasm – Iridophore Optics * Reflection is the superposition of reflected waves * Take just one repeating unit for now

  18. Phasors! Sine wave can be represented by a rotating vector, called a phasor. * Super convenient to keep track of phase differences Animation: http://edumation.org/play_file.php?file_type=animation&file_id=84

  19. Describing a sine wave with phasors 5 2.5 4.33 0

  20. How does the octopus or squid stack up? • We found the color that is most visible. But are other colors (wavelengths) visible too? • How does the number of plates affect how the octopus optics…why not have just one protein plate?

  21. Survey says… More plates = better reflectance More plates = narrower bandwidth Range observed by Ghoshal, 2013 Figures from Land, 1972

  22. Bio-inspired Engineering Block-copolymers photonic gels (Kang, 2007) Solvents modulate de/swelling l = 350 – 1600 nm

  23. Block Copolymers in action Decreasing Salt concentration Figures from Kang, 2007

  24. Electrically Induced Color Change Apply voltage to electrochemical cell Redox Reaction Compression/Expansion  Color change Wallish, 2009

  25. The current state of the art Wallish, 2009

  26. Viewing angle matters: part I Mathger, 2001 Viewing angle Mathger and Hanlon, 2007

  27. Does viewing angle matter? 10o 10o 50o 50o YES! X 2 Cross section of cephalopod a= 10 deg a= 50 deg b a = angle of incidence b = angle of refraction l = 4nd cosb

  28. Non-zero angle of incidence L n1 d2 r n2 Image credit: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/interf.html#c1

  29. References • RE Young, M Vecchione, KM Mangold, 2001. Tree of Life: Cephalopod Chromatophore: http://tolweb.org/accessory/Cephalopod_Chromatophore?acc_id=2038 • LM Mathger and RT Hanlon. Cell Tissue Res (2007) 329: 179-186 • LM Mathger and EJ Denton, J ExpBiol (2001) 204: 2103-2118 • Dan Russel, Penn State: http://www.acs.psu.edu/drussell/Demos/wave-x-t/wave-x-t.html • KM Copper, RT Hanlon, BU Budelmann. Cell Tissue Res (1990) 259: 15-24 • MF Land. Progress in Biophysics and Molecular Biology, 24: 75–106. • Y Kang et al, 2007. Nature Materials, 6: 957-960 • JJ Walish et al, 2009. Advanced Materials, 21: 3078-3081

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