1. OPTICAL MIMICRY AND COMMUNICATION IN CEPHALOPODS ENGN/BIOL 267, Fall 2013 http://symbiol.blogspot.com/

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 Mathger and Hanlon, 2007 Young et al, 2001 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 Cooper, 1990 1um Cytoplasm Protein plates

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

10. What is measured and how? Tissue prep: Thin slice of squid skin Photo Multiplier Tube: Collects light and amplifies Reflected from squid skin Light source with chromatic filter (and polarizer) To computer for data acq. and analysis--.e.g, the reflectance spectra! 1.Choose color of incident light and measure input intensity I inc 2.Measure intensity of reflected light I ref, then compute: R = I ref /I inc

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 Scale bars: 250 nm Cytoplasm Protein plate Convenient Physics model The Real Thing

14. Traveling Waves Wavenumber k = 2  How wave varies in space Frequency f How wave varies with time

15. Different strokes for different folks  Wavelength changes depending on medium in which it is traveling  n o o = n i i = n c c I c o

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

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. 4.33 2.5 0 Describing a sine wave with phasors 5

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 reflectanceMore plates = narrower bandwidth Figures from Land, 1972 Range observed by Ghoshal, 2013

22. Bio-inspired Engineering Block- copolymers photonic gels (Kang, 2007) Solvents modulate de/swelling = 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/Ex pansion  Color change Wallish, 2009

25. The current state of the art Wallish, 2009

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

27. Does viewing angle matter?  = 10 deg  = 50 deg 10 o 50 o 10 o 50 o YES! X 2  Cross section of cephalopod  = angle of incidence  = angle of refraction = 4nd cos 

28. Non-zero angle of incidence Image credit: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/interf.html#c1 n2n2 n1n1 d2d2 L r

29. References  RE Young, M Vecchione, KM Mangold, 2001. Tree of Life: Cephalopod Chromatophore: http://tolweb.org/accessory/Cephalopod_Chromatophore?acc_id=2038 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 Exp Biol (2001) 204: 2103-2118  Dan Russel, Penn State: http://www.acs.psu.edu/drussell/Demos/wave-x- t/wave-x-t.htmlhttp://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