Mimicry in tropical fishes

Abstract

Labroides dimidiatus , a Tropical Wrasse, removes ectoparasites from the bodies, fins, and even the buccal and gill cavities of other fish (figure 1, plate 22). These often show special invitation postures and the ‘cleaner’ occasionally displays in a sort of dance in which the caudal fin is spread and the posterior part of the fish oscillates up and down. Labroides is never eaten even by large predators. Its size, form, coloration, and even its dancing movement are simulated by another fish of a different family, the blenny Aspidontus taeniatus (figure 2, plate 22), who thus succeeds in eliciting the invitation postures from other fish. Being a fin-eater, however, he then attacks instead of cleaning them. The Aspidontus even mimics some local colour-forms of the Labroides . The evolution of the imitative dancing movement of the Aspidontus has been studied in some detail because the evolution of mimicking characters gives the opportunity to study the evolution of a signal produced by a sender alone without co-adaptive interference from the receiver, which in this case does not profit from the ‘false’ communication (Wickler 1963).