Blue-green color of some tailless amphibians is provided by the complexes of the bile pigment biliverdin with proteins serpine, reported in the Proceedings of the National Academy of Sciences. Such complexes are found in different animal tissues outside of cells that is not part of the ordinary chromatophores. Serpina change the reflectance of biliverdin in the body of frogs, tree frogs and other so that they become indistinguishable in color from the leaves of the plants that surround them.
In some animals the integument, or at least part of the blue-green color. This color is achieved either by pigments in special cells, the chromatophores (although sometimes the pigments can lie outside the cells, in the space between them), or due to the structure of surface scales, skin, feathers and other things.
However, a number of blue-green tailless amphibians of chromatophores very small, and the surface of the skin does not involve structural color. Their green color is provided by the presence in the blood of the biliverdin — product of the breakdown of hemoglobin, the main pigment of red blood cells. The person quickly turns into biliverdin bilirubin, and see the high concentration of the first can only in certain pathologies of the liver. But in this case, the content of biliverdin in the blood in people at least 4 times lower than in blood of amphibians, coloring provides this connection. However, if non-green amphibians to enter into the blood biliverdin or some other way to raise its concentration, green they become. So, in addition to this pigment on the coloration of animals is affected by something else.
Biologists from Argentina, Brazil, USA and Ecuador under the leadership of Sarah Bari (Bari Sara E.) from the University of Buenos Aires tried to figure out what role besides giving color plays biliverdin in the body of tailless amphibians, whose painting provided this link, and how to achieve high concentrations. To do this, they examined the tissue samples with a blue-green color have 11 species of the families Hylidae (tree frogs), and Centrolenidae (glass frogs). Scientists have identified them biliverdin and proteins, is able to contact him — serpina. The researchers found their amino acid composition and using knowledge about the relationship of various amphibian species, the biliverdin-binding serpina could look like when I do the frogs in the broad sense of the word. Also, the authors used fluorescence spectroscopy and circular dichroism.
Reflection spectra of different Serbinov that bind biliverdin, has allowed to understand how their complexes regulate the coloration of tree frogs and glass frogs. It turned out that they have a biliverdin-binding Sechenov close to that of the phytochromes and bakteriofagov — protein associated with believeme (bile) pigments and imparts a blue-green color to plants and cyanobacteria, respectively. The result is animals are almost indistinguishable in color from the leaves of plants on which they sit and not only in the visible but also in the near infrared part of the spectrum. The biliverdin-binding serpina, connecting with biliverdin, changing reflection spectra of various tissues of amphibians, so they can masquerade as the surface of various shades depending on need.