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| Sunday, 19 June 2005 |
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Junior Observer |  |
| News Business Features Editorial
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Refined senses : Feeling the world around without touching
Last week, we learned about the novel ways by which animals taste food. Today let's look at how they feel the world around them. As humans, we know we must actually touch something to feel it. This is because our sense of touch is stimulated only by direct physical contact with the skin. Animals however have a sense of touch which is far superior to that of ours. Some even possess a separate yet closely connected sense the scientists refer to as the 'distant touch' which detects vibrations from sources that are very far away. In fact, many animals have incredible abilities to feel the world around them without ever touching anything. Fishes are famous for their ability to sense movement through their skin, using their lateral line system - which is a kind of underwater sonar similar to that used by bats to navigate their way. (The lateral line system was explained in detail in the Junior Observer of May 15).
With the use of this sophisticated navigation system, the fish are able to get a clear picture of their surroundings. For instance, as the fish swims, ripples or waves are created in the water. These travel outward until they come into contact with some object in the fish's surroundings. Then the vibrations bounce back toward the fish and are captured by the sense organs in the body, thereby stimulating nerve connections to the brain which in turn gives the fish sophisticated information about its surroundings. The tiny sense organs which cover the entire surface of a fish's body are known as neuromasts and also serve as normal touch receptors. They respond to physical contact with objects as well as vibrations. In certain primitive fish, such as the African lungfish and the frilled shark, the lateral lines (the horizontal grooves running along each flank to the head) are open. This stimulates the neuromasts not only by reflected vibrations, but also by the movements created as the fish swims. In more advanced fishes or those that live in turbulent waters, the grooves are closed, preventing the neuromasts from being stimulated by the fish's own movements as it swims.This ensures that the sensory organs detect only vibrations reflected from other objects in the surroundings.
The codfish gets a feel of its underwater world with its whisker-like barbels. The male of the Siamese fighting fish is a protective dad. He uses the movements of his large, flowing fins to warn his offspring of any danger. Most fish that live in total darkness within streams in underground caves virtually swim 'blind' and depend heavily on 'distant touch'. The Mexican cave fish has no eyes, but could detect objects smaller than a pinhead using distant touch. They survive in the lightless zones of the deep ocean and find their way in the dark thanks to their hyperdeveloped lateral line system. There are some fish that are known to use their sense of distant touch not only to navigate their way around, but also to communicate, like the male Siamese fighting fish. The fish also use distant touch to synchronize their movements when swimming in large groups. Like fish, spiders too detect vibrations but through the air ... They can do this because they have specialised vibration-sensitive hairs on certain segments of their limbs. These hairs which are able to move in any direction can not only tell the spider the direction from which an object is approaching, but also its size. In fact, these hairs are so responsive to airborne vibrations that they can even detect those caused by the wings of an insect in flight. It may be hard to believe that those in the animal kingdom are equipped with more refined senses than we humans, but the fact is, they certainly are. Imagine being able to really feel something in our surroundings without even touching it! Find out more about the super senses of the animals, because what you learn about their sensitive smell, distant touch, ultrasonic hearing, infrared and ultraviolet vision and unique ways of communication would simply amaze you. |
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