ABSTRACT
In this chapter, the author briefly reviews knowledge of signals in sexual selection in fishes. Fishes utilize various traits as sexual signals, such as sizes of morphological traits, expression of body coloration, and courtship intensity. They consider the benefits derived from mate choice on the basis of each signal. The larger body size of females than that of males in this pipefish may have evolved via both intrasexual and intersexual selection. Crucial benefits and costs for the production of a large body size to signalers remain to be solved in the study of sexual selection. Since the burst-swimming performance may play an important role in evading predators, natural and sexual selection may act in opposite directions for gonopodium lengths in Gambusia males. The relationship between the reproductive success of the cheater males and counter-adaptations by females, i.e., sexual conflict arising from male sexual deception, requires further examination.
