Attraction to conspecific and nonconspecific chemical stimuli in male and female Macropodus opercularis (Teleostei, Anabantoidei)

Abstract

Socially isolated Macropodus opercularis showed a distinct approach response to water taken from the tank of a conspecific individual or a nonconspecific, Trichogaster trichopterus, but not to water from a tank without fish. It proposed that these species produce chemical stimuli which are attractive to M. opercularis. Approach frequency and the total duration of approach during a 10-rain period of stimulation varied with the species and the sex of the stimulus fish but not with the sex of the subject. Subjects responded most frequently to the conspecific male and nonconspecific female stimuli and, least to the nonconspecific male stimuli. Rossi (1969) reported that solitary male Macropodus opercularis (family, Belontiidae; subfamily, Macropodinae) show increased nest building and aggressivity in response to female chemical stimuli. Observations in this laboratory during various experiments on social behavior (Davis, Harris, and Shelby, 1974) confirm that mature 34. opercularis respond to chemical cues from species mates. Water that has contained a female for a period of days can elicit immediate arousal consisting of erection of the medial fins and striking changes in skin color in an isolated male. These are elements of the species-typical responses which are seen in courtship and nest defense (Forselius, 1957; Ward, 1967). In addition, in a situation in which female stimulus water is added slowly through a tube at the water surface, fish approach the incurrent tube and investigate the opening. The approach response occurs even when the behavioral arousal response does not, as when the stimulus diluted with fresh water prior to entering the tank. 1We thank Jessie Shelby for her valuable technical assistance. 2Liem's classification of the order Anabantoidei into four families preferred because it presents a more convincing hypothesis of the natural relationships between the divergent species in this group than does the older classification of Regan (1906).