The Chemistry of Biological Camouflage

Introduction

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I chose to do the chemistry of biological camouflage because I was always interested in how an octopus or chameleon changed its color.  Biological camouflage comes in many different forms.  There’s self-decoration, motion camouflage, and even disruptive coloration.  Although these are interesting, the process of how a chameleon’s skin changes color was far more interesting.  Therefore, I decided to do my project on changeable skin camouflage.

Composition of ...

There are two different processes for changeable skin camouflage.  One process is for vertebrate ectotherms such as fish, frogs, and lizards.  The other is for cephalopods aka cuttlefish, squid, and octopi.  Even though the processes are different, they both have similar components.  Both contain chromatophores which are cells in the skin.  These chromatophores consist of different components.  For example, vertebrate chromatophore cells have iridophores and melanophores.  Iridophores are colorless stackable plates that scatter light to create blue, green, white, and ultraviolet hues.  Melanophores are black, yet they have a huge impact on the vertebrate process.  The melanophore in the chromatophore cell consists of eumelanin, a chemical made by tyrosine.  Tyrosine’s chemical formula is C9H11NO3.  The composition of eumelanin is dihydroxyindole and dihydroxyindole-2-carboxylic acid with pyrrole rings.  Dihydroxyindole or indole’s chemical formula is C8H7N.  Indole is made from coal tar and indigo.  Carboxylic acid’s formula is R-C(O)OH.  A pyrrole ring is wrote out as C4H5N.  

These components all make up the inside of a chromatophore cell in a vertebrate ectotherm.

Now, cephalopods not only have chromatophores and iridophores.  They also have leucophores too which contain guanine.  Guanine is a nucleobase with a formula of C5H5N5O.  Leucophores are white and reflects whatever light illuminates it.  Other than melanophores, iridophores, and leucophores, the main component of changing skin is the chromatophore.


Main Chemicals, Compounds, Components

If there was another main component other than the chromatophore, a melanophore would be the second.  Since chromatophores and melanophores don’t have their own formula, I decided to explain the composition of those two in the paragraph above.  As you know, melanophores are composed of eumelanin which is made of other elements.  The main compounds of eumelanin are indole, carboxylic acid, and pyrrole rings.  The chemical formula for indole is C8H7N and is made from coal tar and indigo.  Carboxylic acid’s formula is R-C(O)OH and pyrrole’s is C4H5N.  All together, the main purpose of chromatophores and melanophores are to control the color transformation of the skin.

Chemistry's Role

In cephalopods, chromatophores contain a pigment filled sac that is surrounded by muscle fibres.  These muscles contract to change the shape of the sac.  This then changes the color of skin in seconds.  If the sac is squeezed the color will rise, stretching out the surface which results in a brighter color.  This expansion makes the color more visible.

Chromatophores in frogs or chameleons contain melanophores which then contain melanosomes. These melanophore cells have long arms that extend to the skin’s surface.  Color change happens when melanosome packets move inside the melanophores. When melanosomes congregate in the center of the cell, the cell turns pale making the skin lighter looking.  When they are scattered, the cell turns dark.  To determine the color of the skin, it all depends on where the arms cross over the chromatophores and the dispersion of melanin.

Color change also happens in leucophores and iridophores.  In vertebrates, the iridophores may change color due to the placing of the platelet stacks in iridophores.  Leucophores can change the color based on where the light hits it.


Background Research

Chromatophores are a naturally made cell.  They are created during vertebrate embryonic development and can be located in the neural crest inside the neural tube.  Melanophores are created inside the chromatophore during embryonic development and are formed when eumelanin (which is made from tyrosine aka an enzyme) is created. Eumelanin is made of dihydroxyindole and dihydroxyindole-2-carboxylic acid with pyrrole rings. All in all, my main components are made naturally.



Resources

http://en.wikipedia.org/wiki/Camouflage

Camouflage: a medley of coloration, materials, or lighting to disguise or make and animal “invisible”

many different methods. Main method is crypsis which means to blend with background. example is fennec fox, horned viper, parakeets

a few more are disruptive coloration (contrast with stripes or spots to break up outline. example is leopard), eliminating shadow (evolving the body to reduce shadow, give a 3D shape, or to look flattened. examples are horned lizard, speckled wood butterfly), self decoration (decorating oneself with the environment. example is decorator crab), motion camouflage (where you stay straight and moving to appear larger. example is a dragonfly), and changeable skin (where body changes pattern or color to blend. examples are chameleon, octopus, and squid. this is the method I am focusing on.)


http://hermes.mbl.edu/mrc/hanlon/coloration.html

Functions of Camouflage:

DEFENSE

communication

attracting mates

signalling an alarm

protection from environment

stalking prey


http://phys.org/news/2013-05-chameleons-creatures-colour.html

Octopi, frogs,lizards, squid, and fish are ectotherms

Have cells with chromatophores

vertebrate ectotherms( frogs, lizards, fish) have three chromatophore cell types.

xanthophores:yellow-red color

iridophores: colorless stackable platelets that scatter light to create blue, white, and UV hues

melanophores: black, are a HUGE factor for color change.

these are large cells that have long arms to extend to skin’s surface

color change happens when melanin pigment (melanosome) packets move in melanophores

melanosomes that congregate in middle of cell produce pale looking skin tones

when scattered it makes skin look dark

depending on where the melanophores cross over chromatophores and the dispersing of melanin, determines skin color

Cephalopods (squid, cuttlefish, octopi)

chromatophores have pigment sac surrounded by muscle fibres

contraction of muscle fibres to change sac form gives an instant color change

two other cells are

iridophores which are the same as vertebrates

leucophores:white


http://en.wikipedia.org/wiki/Chromatophore

Melanophores have eumelanin which is created from tyrosine

Eumelanin chemical formula: dihydroxyindole and dihydroxyindole-2-carboxylic acid with pyrrole rings

key enzyme is tyrosinase

Tyrosine formula= C9H11NO3H5

dihydroxyindole (indole)= C8H7N

Carboxylic acid= R-C(O)OH

pyrrole=C4H5N

volatile and colorless liquid that darkens when exposed to air

Iridophores and leucophores are made from guanine

guanine=C5H5N5O

nucleobase


http://medical-dictionary.thefreedictionary.com/indole

Indole is made from coal tar and indigo


http://ocean.si.edu/ocean-news/how-octopuses-and-squids-change-color

PROCESS:(squid,cuttlefish,octopi) cells called chromatophores control color transformation.Center of chroamtophore contains pigment sac that is balck, brown, red, yellow, or orange.  When sac expands or stretches, the color is more visible. when condensed it is darker. when expanded the color turns brighter.


http://theconversation.com/how-do-chameleons-and-other-creatures-change-colour-13842

Addition to vertebrate ectotherm process

color may also change due to spacing of iridophore platelets.

this happens because the light is scattered in platelets therefore causing the skin to change color


http://tolweb.org/notes/?note_id=2646

Leucophore reflects whatever color of light lights it up


http://en.wikipedia.org/wiki/Chromatophore

chromatophores are found in neural crest in neural tube

created during embryonic development

About the Author
Bailey Ard is a junior at Billings Senior High.  Her main passion is music, but she also loves nature in general which is why she researched this topic.  She plans on going to college for Biology or for music and arts at schools in Oregon, Washington, or Montana.  Bailey also enjoys the ocean and mountains, and she can’t wait to see where her future takes her.
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