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| Sunday, 12 June 2005 |
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Junior Observer |  |
| News Business Features Editorial
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Novel strategies of taste Refined senses
We smell odours when it reaches our nose through the air and taste something when it touches our tongue. But most snakes and reptiles combine the senses of smell and taste. Do you know that when a snake flicks its forked tongue in and out of its mouth, it's literally tasting the air? The snake does not even need to open its mouth to do so.
Collectively they are known as Jacobson's organ. Although mostly found in snakes, it is also common in other reptiles, especially terrestrial lizards. While snakes use the Jacobson's organs to follow trails left behind by mates or potential prey, to recognise the gender of other snakes and to get together for hibernation, lizards use it to find their nests in the breeding season.
In fish that are surrounded by water, particles of scent and taste are both in physical contact with the receptors, so the question arises as to whether they taste or smell. To find the answer to this, it's important to know how the fish's brain is wired. And by studying the neurological connections of the fish's smell and taste receptors, scientists have come to the conclusion that taste is more important to fish than smell because the fish have more nerve connections to taste buds than to smell receptors. A fish's olfactory buds are supplied by only one nerve to the brain but the taste buds are supplied with branches of three different cranial (skull) nerves.
The channel catfish has taste buds in its entire body with most of them located on the whisker-like barbels around its mouth. Research has revealed that these particular taste buds which are extremely sensitive could detect certain proteins in water at concentrations as low as 1-100 micrograms per litre. Then there is the novel strategy of taste from the insect world.... insects that taste food with their feet! We all know that butterflies have feet that can sense sweetness.
The blowfly too has taste buds not only in the mouthparts, but also in its feet. These taste buds become more sensitive to sugars when the fly is hungry. No matter where the taste sensors of an insect are located, they normally take the form of hair-like structures known as taste hairs. Each one usually comprises five neurons (sensory nerve cells) at its base and four of these are concerned with taste. Of these four neurons, one always responds to sugar, one to water and the other two to various salts.
However they do not actually eat the food until the taste buds on these and other mouth parts analyse whether it is suitable to eat or not. Now you know that not all animals taste food with their mouth like we, humans do. Isn't it amazing to learn food could be tasted even with feet? |
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| Politics | Produced by Lake House |
In the human world, we know our sense of taste, for food comes from the
taste buds located in our tongues. But, in the animal Kingdom, it's an
entirely different story. You'll be amazed to learn that there are novel
strategies that have evolved for creatures to sample the flavours of the
world around them; from flies and bees that taste with their feet, to fish
that use their whole body as a tongue to taste the water they swim in! 
It can flick out its tongue through a small hole in its lips and
collect scent particles from the air or from a nearby object such as a
stone. On the roof of the snake's mouth is a pair of domed pits which have
a moist lining that is sensitive to the chemicals it has picked. Back
inside the mouth, the tongue's fork are pressed to these domed pits and
the olfactory particles are transferred to the pits, which are well
supplied with nerve endings. 
When it comes to fish, scientists debate as to whether fish smell or
taste the water around them. This debate springs from a theory about the
two senses. Smell is usually defined as the detection of chemical signals
from distant sources whereas taste implies direct contact with the
animals' chemoreceptors. 
And where do you think a fish's taste buds are located? Not necessarily
in the mouth like in land vertebrates. A fish's taste buds could be
anywhere. You may be surprised to learn that the long, slender fins of
many species have taste buds at their tips, enabling them to taste food
just by touching it! In certain fish, the distribution of taste buds have
gone to extreme limits, making them literally 'swimming tongues'. Fish
such as carp, mullet, cod and sturgeon have taste receptors almost all
over their bodies. 
Did you know that when they have been searching for food for long, and
are starved, they could detect sugar diluted in water down to
concentrations as low as 0.003 per cent using their feet? This is a
sensitivity which is 200 times greater than that of the human tongue.
Honeybees too have taste buds which are hypersensitive to sugar. 
Having taste buds on their feet is certainly an advantage for insects
because they often land feet first. If they land on any potential food and
sugar is detected by the taste hairs on their feet, the message is
automatically passed on to the brain, stimulating the insect to put the
food in its mouth. Butterflies do so by extending their proboscis and
blowflies their labellar/lobes. 
