Natural History and its unsolved mysteries

                                        Chameleon : The colour changing species

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Dr. Jagadindra Raychoudhury

WhatsApp Image 2022-04-12 at 8.07.10 PM

Nature has luminously decorated the world with a mixture of habitats, comprising of flora and fauna which are totally unrivaled with any other invention of human being. We can spend hours together in an around nature without thinking of hungriness or feelings of dehydration but the situation has been reversed with a remarkable speed by destroying natural recourses for the pseudo progress of mankind towards development. The state of affairs happened to occur only for the greediness of human being. However, without the bed of nature people will never survive for a long time. A handful of nature lovers always try to raise their voices for the conservation of nature and sometimes government machinery also extends their help, but a strong legislation is also required for protection of nature especially for the welfare of future generation.

            Many flora and fauna have already become extinct, some are endangered and others are vulnerable yet few species still survived with their entire trait intact. I will try to express one of the lizards which is very popular due to its charismatic changing of colour and the species is none else but chameleon. Chameleons are a distinctive and highly specialized clade of old world lizard with 202 species described as of 2015. Chameleons have their long, sticky tongue; and their eyes, which can be moved independently of each other. Chameleons are under the Class of –Reptelia, Family- Chamaeleonidae and Order- Squamata.

            It is to be noted that chameleons have some specific characteristics besides changing their colours. They are distinguished by their zygodactylous feet, their prehensile tail, literally compressed bodies with casqued head, projectile tongues along with swaying gait. They also have a horn or crest on their brow and snout. The eyes of chameleon are of independent nature with mobility where two separate individual images formed and that is analyzed by the brain for its environment. The eyes are able to move laterally 180 degree and vertically 160 degree.

            Chameleons are mostly arboreal; their compressed body helps in adaptability generated for climbing and visual hunting. The practice of climbing is also adhered to their prehensile tail which supports the stability especially during movement while on a branch in the canopy; hence it is often referred to as ‘Fifth limb’. Chameleons live in warm habitats that range from rainforests to desert like conditions where various species are available in Africa, South Europe, Madagascar and Southern Asia.

            The most vital feature of chameleon is changing of skin colors and this coloration varies from species to species. The colour combination spark on chameleon is blue, pink, red, orange, green, black, brown, yellow and purple etc. The skin colours are changing because of a superficial layer present on the skin which contains pigment and under the layer, a small cell is present with guanine crystals. The tuning, by an unknown molecular mechanism, changes the wavelength of light reflected off the crystals which changes the colour of the skin. It is to be noted that chameleon colour palettes have evolved through evolution and the environment. Chameleons living in the forest have a more defined and colourful palette compared to those living in the desert.

The most important observation on chameleon is related to the reason behind why they change their colour? It is due to social signaling and reactions to regulate temperature. It’s a physiological change, either to a darker colour to absorb light or to a lighter colour to reflect light and heat to stabilize or lowering their body temperature. Mostly, chameleons tend to show brighter colours displaying aggression to other chameleon and on the other hand darker colour when they submit or ‘give up’. It is to be noted that some other species especially in Madagascar and South Africa have their blue florescence in their skull tubercles.

            The feeding habits of chameleons are something special because of their technique. No doubt, they are normally insectivores but for capturing food they use their long tongues from some distance away. This method is possible because chameleon’s tongues are two times longer than their bodies. The long tongue consists of highly modified hyoid bones has an elongated, parallel sided projection, called the entoglossal process, over which tubular muscle, the accelerator muscle sits. The drawing back of tongue into the mouth could be possible due to hyoid and accelerator muscle. The thermal sensitivity of tongue retraction is not a problem because chameleons have very effective mechanism of holding into their prey once the tongue has come into contact with it because of wet adhesion and interlocking and suction.

            Besides chameleon, there are many more species with differences in their features ranging from terrestrial to aquatic, even in snow bedded mountain. The amazing nature of various species which attracted to us are losing their habitat for the hardcore encroachment of human being for their unwanted need. This greediness of acquiring more land in every aspect indirectly reflects in the extinction of many more species from this planet.