At a choice of fish in shop we are guided by her price and the taste. Unlike penguins we know taste of fish, but whether fish knows taste of food? As well as at us, and at all vertebrata, at fishes five sense organs, including flavoring receptors. However they essentially differ from ours. 
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Placement of receptors of fish is not limited to language and a mouth. Fishes can feel taste lips and even a body. Thanks to an abundance of receptors flavoring feelings at fishes are much richer than ours. For example, minnows distinguish tastes of various carbohydrates. If for us any sugar sweet, just as "when candles are out all the cats are gray", these fishes distinguish sucrose from glucose or lactose.
For work of flavoring receptors moisture is necessary. The dry food «does not climb in a mouth» including for the reason that it is impossible to feel its taste. Fishes of a shortcoming of moisture do not test, they live in water therefore their receptors of taste can be found not only in a mouth, but also on sides and fins.
We unable to estimate convenience of such approach to an assessment of quality of food. For certain and to us it would be convenient to touch food with a finger instead of dragging that попадя in a mouth. Fishes actively take the advantages, flavoring receptors are necessary to them not only for an assessment, but also for food search.
While land animals "prefer" to rely on sense of smell, fishes in search of food "try" everything. To estimate taste, they should not chew or swallow, it is enough to touch potential food with a fin, lips or other part of a body.
Exactly for this purpose catfishes rummage in benthonic silt, lifting garbage clouds. On bodies of these fishes, including on long flexible short moustaches, hundreds thousands flavoring receptors. Ichthyologists from the Moscow state university together with the Norwegian colleagues counted them 680000. Compare quantity of receptors of a catfish to our "pity" 5-9 thousand moreover and hidden deeply in a mouth.
Having appeared in silt clubs, the catfish feels a food all the body, it will not escape the uniform slice suitable in food. Strategy, so effective for benthonic feeding on shoal, is applicable even in ocean depths.
Fishes grenadiers – dominating predators and padalshchik of numerous ocean pools on the most part of a planet. International team of researchers from Great Britain, the USA and Germany interested, why they "like" to swim headfirst?
It appeared that without refusing completely search of food in a smell and sensitively reacting to the chemical irritants dissolved in water, in short distances grenadiers prefer to look for food to taste. In their skin and moustaches about 20 thousand receptors-aksonov analyzing taste of everything what touch, and transferring data to other nervous cages are located.
According to researchers, search of food in a smell on small removal from it appeared ineffective that caused "change-over" of touch perception and formation of features of the behavior promoting careful check of surfaces at small speeds of swimming in grenadiers. Without having fingers, grenadiers feel a bottom moustaches, unmistakably finding a food to its taste.