Shapeshifters of Nature: Colour-Changing Camouflage

As I am sure many of you are aware, a lot of species of animals have what seems to be an almost magical ability to change their colour. An ability that allows them to camouflage with their surroundings, protect themselves from predators, or even hide from prey. These colour-changing camouflagers have a wide variety of types, ranging from seasonal to immediate- seasonal colour changers like arctic foxes, hares, etc, and, more immediate or situational colour changers like octopi, cuttlefish, and chameleons.?

Seasonal-

Over 20 species of birds and mammals distributed across the northern hemisphere undergo a complete, biannual colour change from brown in the summer to completely white in the winter. Renowned for their quick-changing abilities, these animals retain their brown, grey, or black fur/feathers in the summer and strategically shed their coats in the winter to become white as a ghost, in turn helping them blend entirely into their snowy surroundings and hide from predators. These include animals like Hares, Arctic Foxes, Peary caribous, Ptarmigans, Siberian hamsters, Collared lemmings, Ermines, Weasels, etc.?

Immediate-?

Immediate colour changers, on the other hand, are a bit more interesting. They merely change their coat/skin pigments to match their surroundings. These animals end up altering their color by moving pigments within cells called chromatophores leaving factors like the amount of pigment in the cell, and how it's distributed to determine the color of the creature's skin. This helps them hide from predators, or even prey as they prepare to attack. Let us look at some examples in detail.?

Several species of octopuses can change colours, but the one that does it best is the mimic octopus. It can change its colour to mimic its surroundings by expanding and contracting its pigment cells and changing the shape of its body to mimic other animals and plants. Many species of squid also change colour by expanding and contracting their pigment cells. Cuttlefish, similar to octopuses and squids follow the same mechanism but can do it in utter still darkness.

Another few examples include seahorses, an incredible species that perform the same miraculous feat during courtships, the peacock flounder that changes colours by releasing pigments in certain cells and restricting them in others to make a pattern resembling that of the surface it is resting on and the super-sleek unicornfish that shifts from dark blue to light blue when smaller fish try to clean it. Scientists believe this color change makes it easier for the tiny cleaner fishes to spot the parasites on their scales. Some species of unicornfish also change colour during mating rituals.?

Chameleons are world-renowned for their ability to change colour, but contrary to popular belief, they don’t do it for camouflage. Instead, they change colours to show their mood- whether they’re feeling territorial, aggressive, or ready to mate. They achieve this using the same types of specialized cells found in octopuses and cuttlefish. Tree frogs also change similarly but do so to either camouflage themselves or to change with the temperature. If they need to absorb more heat, they turn a darker colour and vice versa.

As its name suggests, the golden tortoise beetle is typically gold in colour. However, when stressed, it turns red. This shiny gold appearance comes from liquid filling tiny channels in its exoskeleton and when the beetle is under stress, the liquid moves, exposing a deep red colour underneath. Female white-banded crab spiders also often change colour to match their background. They do this to match the colour of a flower and lay in wait to catch their bamboozled prey.

Mechanism-?

For seasonal changers, as discussed earlier, coats in warmer months are usually earthy colours like brown, grey, black, etc. But in the colder months, they slowly shed their previous fur or feathers and grow white ones that help them camouflage into the snowy surroundings. When the days get shorter and nights longer these animals receive hormonal signals that trigger this change in their coats. It is also said that photoperiod, or the amount of light received during the day, may have a significant influence on this change, forcing their brain to send signals to the chromatophores and change the colour of their new coat. The space left by the absence of pigment in the white coats leaves pockets of air that end up providing better insulation during these harsh climates.

When it comes to immediate changers, in vertebrates such as frogs, lizards, and fish, there are three main types of chromatophores: xanthophores which contain yellow-red pigments; iridophores which are colourless crystals that refract light to produce white, blue, and violet shades and melanophores which have black melanin pigments. Colour change happens when melanin pigment packets, called melanosomes, move within specialized cells known as melanophores. When the melanin is concentrated in the centre of the cell, the skin looks very pale. However, when it spreads out through the cell’s extensions toward the skin’s surface, the animal appears darker. This colour can also change when the melanophores extend over the other colour pigments and cover or reveal them.?

In animals such as cuttlefish, the mechanism is a little different. Cephalopod chromatophores contain a sac filled with pigment, surrounded by radial muscle fibers. When these muscles contract, they alter the size and shape of the sac- flattening it into a thin disc or compressing it into a small sphere, allowing for rapid and dramatic colour changes. Beneath the chromatophores, cephalopods have two additional types of cells: iridophores, which function similarly to those in vertebrates, and leucophores, which appear white. When the pigment sacs contract, these underlying cells become visible, further influencing the colours displayed.

Conclusion-?

Nature is full of incredible adaptations, and these magical colour-changing abilities are among the most fascinating ones. They have an amazing, almost supernatural display of ability. These shapeshifters of nature ultimately showcase the remarkable ways animals have evolved to thrive in their ever-changing environments.