The olfactory system of fishes is capable of recognizing and discriminating a large

number of odours in the surrounding waters. Although fish inhabit an aquatic envi-
ronment, their olfactory systems share many common characteristics with those of

terrestrial vertebrates. In fishes, the discrimination of water-soluble odours is very

important for several life functions such as feeding, reproduction, kin recognition,

escape from danger and migration. To accomplish these functions, the olfactory sys-
tem of fish detects many odorant substances including amino acids, nucleotides,

steroids, prostaglandin and bile acids. This olfactory chemoreception is accom-
plished through binding of the odorant substance to an olfactory receptor (OR) in the

olfactory epithelium with subsequent propagation of the information to the central

nervous system.

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