Fish have both a sense of smell (olfaction) and a sense of taste
(gustation). The two senses are governed by different sense cells. In
the water, both senses act at a distance. Gustation is supposed to be
more specific as a chemical sensor than olfaction. The articles, the
books and links I looked up uniformly say that olfaction acts at a
distance while gustation acts at close range.
To me, gustation in fish is the most mysterious sense.
Olfaction in fish is clearly associated with with organs (nare) that
are homologous to the olfaction organs (nostrils)in mammals. However,
fish "tongues" are bone structures that have no taste buds. The fish
tongues are not homologous to mammalian tongues, and mammals have
nothing like them. The taste buds of mammals are restricted to the
tongue (a...