Asymmetric species specificity in reponses to female sexual pheromone by males of two species of Trichogaster (Pisces: Belontiidae)

Abstract

We examined the species specificity of the responses to female pheromones by males of Trichogaster trichopterus, the blue gourami, and Trichogaster pectoralis, the snakeskin gourami, sympatric belontiids from Southeast Asia. Using only chemical signals, males of both species discriminated between ripe females and nonripe females, suggesting that the female chemical signal functions in reproduction. Trichogaster trichopterus males also discriminated between and nonripe females and plain water. Two different experimental procedures showed that male T. pectoralis discriminated between chemical cues from conspecific and heterospecific females while male T. trichopterus did not. This asymmetric specificity of male response is consistent with the ecological histories of the experimental stocks. Trichogaster trichopterus used in these experiments came from a population historically isolated from congeneric species, while T. pectoralis came from a population originally sympatic with three congeners.