My Science School

Thousands of years ago all species of animals lived in the wild and roamed our planet freely. However, centuries ago, humans domesticated some species for their own benefit. This list is fairly endless from dogs, donkeys, camels, and horses to cattle, sheep, pigs, and goats. In the 19th Century, naturalist Charles Darwin was among the earliest to detect something interesting about these animals "different species often developed similar changes when compared to their ancient wild ancestors”. How could that be? Come, let's find out.

The set of shared changes seen in domesticated animals is referred to as "domestication syndrome". And, for long, one of the main reasons for this was attributed to the tamer behaviour of domesticated animals. It is understandable that our ancestors would have selected calmer animals of the lot for domestication, and so, this trait continued in the subsequent generations too, irrespective of the species. Some of the noticeable changes are "shorter faces, smaller teeth, more fragile skeletons, smaller brains, and different colours in skin, fur, and feathers". (Remember, not all species display all the changes. A few species may share several of these changes while some may share just a few. But all of them seem to display at least a few changes.)

One of the theories associated with tamer behaviour is that it "somehow triggered all of the other traits too". Another theory states that "selection for tameness causes the other features because they're all linked by genes controlling neural crest cells. These cells, found in embryos, form many animal features-so changing them could cause several differences at once". However, a new hypothesis by researchers suggests that these theories are over-simplified and do not offer the complete picture. They say the "removal of pre-existing selection" is as important as tameness. For instance, domesticated animals may not face the threat of predators, and "so wild traits for avoiding them might be lost. Similarly, competition for mating partners too comes down, bringing down "wild reproductive features and behaviours". Since domesticated animals are provided food, this could change not just their "metabolism and growth" but even their features over a period of time.

The researchers argue that several selective changes are at play when it comes to the characteristics of domesticated animals, not just "selection for tameness".

Picture Credit : Google 

Glass frogs live on trees, are active at night, and many of them are difficult to spot because of their green skin that merges well with their environment. "But these amphibians become true masters of camouflage during the day when they're asleep." How? Come, let's find out.

When glass frogs rest or sleep, their muscles and skin turn transparent. So, whats visible are their eyes, bones, and internal organs. It is hard to spot them because they sleep on the bottoms of huge leaves and also blend well with the environment due to their transparency. But, how do they turn transparent, and what about the visibility of blood? Red blood cells absorb green light (the colour of light usually reflected by plants and other vegetation), and reflect red light. This makes blood highly visible, especially against a bright green leaf. In the case of glass frogs, though, something extraordinary happens.

A research team recently "observed that red blood cells seemed to be disappearing from the circulating blood" when the frogs rest. They conducted additional imaging tests on the animals, proving via optical models that the animals were able to achieve transparency because they were pushing red blood cells out of their vessels. It was suspected that the cells were being stored in one of the frog's inner organs. which are packaged in a reflective membrane.

To find out where exactly the blood was going, scientists used a non-invasive imaging technology called photoacoustic microscopy (PAM). And the result was startling. The primary result is that whenever glass frogs want to be transparent, which is typically when they're at rest and vulnerable to predation. they filter nearly all the red blood cells out of their blood and hide them in a mirror-coated liver - somehow avoiding creating a huge blood clot in the process." When the frogs "are awake, stressed or under anaesthesia their circulatory system is full of red blood cells and they are opaque". This unique capacity would explain why there are hardly any other land-based vertebrates that can achieve such transparency.

Also, in "most animals, pooling blood together leads to clotting which can be life-threatening, for example = leading to heart attacks in humans". So, studying these amphibians can even help us understand blood clotting better.

Picture Credit : Google