Rockin' shrimp give dance signals to parasite-laden fish | Science Blog:
Using underwater field observations in conjunction with behavioral experiments, researchers have discovered that a small crustacean, the yellow-beaked cleaner shrimp, performs a specialized dance that affects the behavior of large, predatory client fish. This signaling represents shrimp-to-fish communication that allows both hungry cleaner shrimp and parasite-laden client fish to benefit from a non-predatory, "cleaning" interaction.
The cleaner-client relationship between the shrimp and the fish fulfills many criteria of an economic market, and in this context the shrimp's signals essentially represent "advertising." The work is reported by Justine Becker and colleagues at the University of Queensland.
These signals are evolved, and have to continue evolving to avoid dishonesty.