When the words "chameleon" or "octopus" immediately arises an association with bright colors that change each other. Green foliage and grass, multi-colored flowers and fruits, a variety of colors of aquarium fish and amazing coloring of animals. All this is the world that surrounds us. Living organisms owe this multicolor to special cellular structures - chromatophores. What are these strange formations, what is their function and how do they work - this article is about this.
Color carriers
This is how the word "chromatophores" is translated. What is this substance, it is worth explaining in accordance with the various groups of living organisms. In crustaceans, mollusks, fish, amphibians, reptiles, these are light-reflecting cells and cells containing pigment. They are responsible for the coloration of the eyes and skin and are formed only during embryogenesis in the neural crest. Afterduring the ripening period, they spread throughout the body. By tone in white, they are divided into cantophores (yellow), erythrophores (red), iridophores (shining), leucophores (white), melanophores (black or brown). The structure of the chromatophore is different for different groups, and we will return to this issue below.
Photosynthetic plastids
What are algal chromatophores? These are single-membrane organelles of brown and green algae, ribbon or star-shaped, containing colored granules (chlorophylls and carotenoids). In microorganisms and bacteria, these are membraneless organelles of various shapes and purposes. For example, the chlamydomonas chromatophore is represented by a chloroplast in the form of a bowl (starch is stored in it) with a red pigment body containing hematochrome (red pigment). Thanks to him, this protozoan has the ability to sense light. In the unicellular alga Chlorella, the chromatophore is represented by granules of chlorophyll-a and chlorophyll-b, floating in large numbers in the cytoplasm of the cell. With their help, this alga performs the most efficient photosynthesis from a minimum of resources. Thus, for protozoa and unicellular algae, it is characteristic that, in addition to the photosynthetic function of the chromatophore, it is storage and photosensitive. It is worth noting that the chromatophores of algae differ from the chloroplasts of higher plants in a simpler structure and other types of chlorophyll (a green pigment with a magnesium complex).
Pigmented animal cells
UHumans and many animals have cells that contain only one pigment, melatonin. These cells are found in the skin, wool, hair and feathers, in the iris and retina of the eyes. Color saturation depends on concentration. These cells are called chromatocytes, they are formed throughout the life of the body and can only be of one type - melanocytes.
Specific work
What are chromatophores? The idea of their work, which is necessary for their classification, was formed in the 60s of the last century. The latest data in biochemistry have not changed these provisions, but have clarified the principles of their work. There are two types of chromatophores: biochromes and chemochromes. The first are true (real) pigments - carotenoids (various derivatives of carotene) and pteridines. They absorb one part of the visible light and reflect the other. Structural colors (chemochromes) produce color through interference or scattering (reflection of one wavelength and transmission of another wavelength).
Color classification
The division of chromatophore by color is rather conditional. And that's why. Xanthophores and erythrophores can be contained in the same cell, and then its color will depend on the amount of yellow and red pigments. Iridophores are chemochromes containing crystals of guanine. It is the crystals that reflect light and give an iridescent color. Zumellanin melanophore is highly light absorbing and produces black and brown colors.
The biological role of pigments
Melanin is the most common pigment in living thingsorganisms - due to the absorption of light, it performs the functions of a shield cell. It does not transmit ultraviolet rays into the deeper layers of the skin, protecting internal tissues from radiation damage. The role of pigment in the mechanisms of adaptability of living organisms cannot be underestimated. Everyone knows what a chromatophore is in the life of pollinating insects and plants pollinated by them. Body color plays an important role in defense against enemies, tracking prey, warning of danger, and reproductive behavior. Chlorophyll, bacteriorhodopsin are photosynthetic pigments, and hemoglobin and hemocyanin are respiratory chromogens.
Property to change
The most interesting and mysterious phenomenon is the color change of some animals. This phenomenon is called physiological color change. This mechanism is complex and continues to amaze scientists. Quite a few representatives of various phylogenetic branches acquired this ability in the course of evolution. Chameleons and cephalopods (octopuses and cuttlefish) are organisms quite far from each other in the evolutionary ladder of life, but the undisputed leaders in the ranking of the most "changeable". This is surprising, but the mechanisms of operation of chromatophores are the same for them.
How do they do it
Some cephalopods, arthropods, crustaceans, fish, amphibians and reptiles have cells that are elastic like rubber under their skin. Their chromatophores have a membrane and are filled with paint, like watercolor tubes. Each such cell at rest isa ball, and when excited, a disk stretched by a multitude of dilator muscles (dilators). They stretch the chromatophore, increasing its area many times, sometimes sixty times. And they do it very quickly - in half a second. In chromatophores, pigment grains can be located in the center or scattered throughout the cell, they can be many or few. Each dilator is connected by nerves to a command post - the animal's brain. Color changes occur under the influence of two groups of factors: physiological (changes in environmental factors or pain) and emotional. Fear, aggression, sympathy for the opposite sex and intense attention - all these emotional experiences change the color of the animal.
Process Cytology
When the animal is at rest, all pigment grains are in the center and the skin becomes light (white or yellowish). It is this frosted glass that looks like a cuttlefish with a black spot of an ink bag. When the dark pigment is in the branches of the chromatophore, the skin becomes dark. The combination of pigments of different layers and gives the whole range of shades. The green and blue colors result from the refraction of light in guanidine crystals in the upper layers of the skin. Skin color can change quickly and take over the entire body or parts of it, sometimes creating a very bizarre pattern. In addition, the chromatophores themselves can descend into the deep layers of the skin or rise to the surface.
Chief commander - eyes
Scientists have established a close relationship between vision andcolor change. Light through the organ of vision affects the nervous system, and it gives signals to the chromatophores. Some are stretched, others are contracted, and at the same time, maximum matching of masking colors is achieved. Interestingly, even a blinded octopus can change color - it also perceives color with suckers, and if at least one remains, the octopus will change color. It's amazing what bizarre patterns he can repeat on his body. There is evidence that the octopus was able to reproduce the text of the newspaper in seconds, which was next to the aquarium. And it looks like mysticism.
Some interesting facts
In addition to the amazing ability of octopuses and chameleons to change color, they also have a few more amazing features that you did not know about.
The brain of an octopus is the most developed among invertebrates. The largest octopus weighed 180 kilograms. It was 8 meters long (caught in 1945). Some octopuses can walk on land using their tentacles.
One of the most poisonous animals on the planet is a deep-ringed inhabitant of the Indian Ocean. After its bite, a person dies within 1.5 hours. And there is no antidote.
The smallest chameleon, the Madagascar Brookesia, is less than 3 centimeters in size, while the largest, the Malagasy, grows up to 70 centimeters in length. They are practically deaf, but will see the smallest insect at a distance of 10 meters. The angle of their vision is 360 degrees, and each eye sees its own picture of the world.
