OPTICAL MIMICRY AND COMMUNICATION IN CEPHALOPODS ENGN/BIOL 267, Fall 2013
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Transcript of OPTICAL MIMICRY AND COMMUNICATION IN CEPHALOPODS ENGN/BIOL 267, Fall 2013
OPTICAL MIMICRY AND COMMUNICATION IN CEPHALOPODS
ENGN/BIOL 267, Fall 2013
http://symbiol.blogspot.com/
Master of Camouflage
Where’s Waldo…err, the octopus?
Cuttlefish Camouflage
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
Chromatophores: Pigment Sacks
Mathger and Hanlon, 2007 Young et al, 2001
• Variable size/radius• Under muscarinic control• Color spectrum somewhat limited
Chromatophores in Action
http://blog.backyardbrains.com/2012/08/insane-in-the-chromatophores/
Iridophores: Reflectors
* Stacks of protein plates (reflectins) in cytoplasm
* They are, by themselves, colorless
* Located beneath chromatophores
Cooper, 1990
1um
CytoplasmProtein plates
Iridophores are active
*Spacing between layers can change.
•* Changing layer spacing implies changing reflected wavelength
•* Under neural and chemical control (Ach)
Cooper, 1990Scale bars: 250 nm
Cytoplasm
Protein plate
Mathger, 2007Cooper, 1990
What is measured and how?
Tissue prep:Thin slice of squid skin
Photo Multiplier Tube:Collects light and amplifiesReflected 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 Iinc
2. Measure intensity of reflected light Iref, then compute: R = Iref/Iinc
Two to Tango: Chromatophore-Iridophore Interaction
Yellow chromatophore+ green iridophore = dark yellow
Yellow chromatophore + red iridophore = orange!
Biomimicry in Cephalopods: Part Deux
1um
Application of Optics
Scale bars: 250 nm
Cytoplasm
Protein plate
Convenient Physics model The Real Thing
Traveling Waves
Wavenumber k = 2 /p l How wave varies in space
Frequency fHow wave varies with time
Different strokes for different folks
Wavelength changes depending on medium in which it is traveling
nolo= nili = nclc
lI
lc
lo
Wavelength changes depending on material/medium
air cytoplasmiridophore
Cytoplasm – Iridophore Optics
* Reflection is the superposition of reflected waves
* Take just one repeating unit for now
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
-0.2 0 0.2 0.4 0.6 0.8 1 1.2-6
-4
-2
0
2
4
6
Time (sec)
v(t)
[Vol
ts]
v(t) = 5 cos(2ft) with f = 4 Hz
4.33 2.5
0
Describing a sine wave with phasors
5
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?
Survey says…
More plates = better reflectance
More plates = narrower bandwidth
Figures from Land, 1972
Range observe
d by Ghoshal, 2013
Bio-inspired Engineering
Block-copolymers photonic gels (Kang, 2007)
Solvents modulate de/swelling
l = 350 – 1600 nm
Block Copolymers in action
DecreasingSalt concentration
Figures from Kang, 2007
Electrically Induced Color Change
Apply voltage to electrochemical cell
Redox Reaction
Compression/Expansion
Color change
Wallish, 2009
The current state of the art
Wallish, 2009
Viewing angle matters: part I
Mathger and Hanlon, 2007
Mathger, 2001
Viewing angle
Does viewing angle matter?
a= 10 deg a= 50 deg
10o
50o 10o
50o
YES! X 2
b
Cross section of cephalopod
a = angle of incidenceb = angle of refractionl = 4nd cosb
Non-zero angle of incidence
Image credit:http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/interf.html#c1
n2
n1
d2
L
r
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 Exp Biol (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