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The Invisible World

The Invisible World

By Dr. Priyadarshini Chakrabarti (Basu) (Post Doctoral Researcher, Oregon State University, USA)

Nature in all its bounds and glory have harnessed the world in a tight leash – a leash so sensitive that the slightest maneuver may upturn the harmony of existence! The ecosystem services that we benefit from are priceless, vast and unthinkable. Water that we drink, timber that we collect, food that we receive, the air that we breathe are very few examples of nature’s benevolence. But how many of us are really aware of the fine things carrying on endlessly right in front of our very eyes? We hardly take notice of the extremities and hardships in the animal kingdom and the aids provided by nature to them to survive, to rise.

Part 1 – Do we really see what we see?

Often vision can be misleading! “Seeing” is necessarily not “believing”! We see that bright flowers bloom – buzzing with pollinators! Insects scampering around for nectar rewards! Have we ever thought precisely what guides them to the spot? We apparently see a bright yellow flower – plain yellow with no specialties – yet the bees know exactly where to look for nectar. This is where our eyes fool us! Flowers have beautiful designs called “honey guides”. These are guide marks formed by pigment patterns in flowers to guide pollinating insects to the centre of flower where sex organs and nectar are present. These marks are particularly prominent in bee flowers taking up variety of dots and patterns. Mostly honey guides are invisible to the naked eye and visible only under ultraviolet light! Yet insects can readily see them.

Royal Society had once exhibited images that illustrated what animals see – how the world looks so differently to them and us! The fascinating insight showed that a large number of animals see in ultraviolet – hence their vision is a lot different than ours. What we see and what we think they see are quite different from what they actually see.

Birds, for example, can see ultraviolet. A peacock, looking for potential mate, sees plainer images (not the rainbow of greens and blues that we see) but more brightly coloured and prominent display of the eye spots in plumage! Chysina beetles or ‘jewelled scarabs’ reflect light that humans can’t see. It is circular polarised light – very bright yet invisible to the human eye! Scientists suspect it might be used for communication (perhaps mating) but they are yet to unlock its mysteries!

It has also been thought that small animals see in slow motion. Research is still going on as to what “critical flicker fusion frequency” really is and how it helps small animals evade predators. “Critical flicker fusion frequency” essentially measures how fast the eye can process a blink of light. Small animals have now been studied to have critical flicker fusion frequency much higher than ours. This perhaps helps them to avoid danger by responding faster.

To sum it all up – we think we see the world clearly. Have we ever wondered how sharp the hawk spots its prey soaring in the clouds? Have we really wondered what we think we see may actually look different to the rest of the animal world?

Part 2 – What’s cooking?

This is perhaps our favourite question when we smell something enticing to our taste. We credit ourselves with the ability to smell rotten eggs and the finest perfumes with equal dexterity. Yet what happens in an environment when animals are too small to see far? Or when vision has been obstructed? Mother Nature has yet another trick up its sleeve – the pheromones! Pheromones are secreted or excreted chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual of the same species.

Each species has its unique combination of chemicals – like lock and key mechanisms! Pheromones in a particular species are also diverse – varieties ranging from mating to alarm to recruitment pheromones! When a trail of ants move in a dense forest, vision is often not the weapon of choice – they rely on smell instead. If a falling leave or rock disrupts this trail, it is “smell” that gets them back on track. Identifying nest mates would not have been possible for bees if pheromones did not help! Recruiting soldiers for battle also requires pheromone! Finding way to food, bowing to the queen of hive, battling enemies, identifying nest mates – all depends on the keen sense of smell!

We all have seen and heard about dogs sniffing out bombs and drugs, cats sniffing out mice! Animals are indeed capable of finer senses and nature has provided bountiful! But what happens elsewhere – how do animals living in harsher climate out compete humans in survival?

Part 3 – Alone in the dark

It is easy to smell in the wind and see in the light. What happens if there is constant darkness and wind is replaced with billions of gallons of sea water? What happens to the deep sea creatures where no light penetrates and the water is cold – very cold? Some species have evolved extraordinary eyes for better vision while others very precise sense of touch. For instance, the giant squid copes with low levels of light by having enormous eyes. Other creatures detect their prey by sensing vibrations instead of by seeing them. With no primary food source available, the deep sea inmates rely on a slow, steady shower of waste food particles from above, or hunt and scavenge in the darkness.Many species in the twilight zone and below produce their own light, called bioluminescence, which they use to find potential food and mates. Their bodies have become well adapted to withstand tones of water pressure mounting on them each day!

Without sunlight, the animals have evolved a range of adaptations. From being blind to being armed with clever baits for attracting the sighted, these species have developed a variety of survival techniques.

These are very few instances of animals being able to sense – see, smell, feel – better than us humans! The world that we see has treasures hidden in plain sight. Yet we fail to notice it. This invisible world has long been unseen for our ignorance. Research is unveiling new prospects every day and what nature needs are flag bearers of environmental protection. Gratitude alone for all of nature’s resources will not suffice. It is time to conserve, preserve and rebuild. It is time for positive action. It is time to take notice, not just see; feel, not just observe and guide, not just utilize!


Pollination Biology by D.P. Abrol, Springer Publications