Effects of induced triploidy on aggressive display in the fighting fish, Betta splendens Regan

Abstract

Triploidy was induced in the fighting fish, Betta splendens Regan, by varying all possible combinations of temperature (37-41°C), time after insemination (2-3min) and shock duration (2-4 min). Heat shock at 39°C for 3 min duration initiated 2-5 min after insemination gave high frequencies of triploids (86%) as assessed from chromosome number and red blood cell nuclear volume. There was no significant difference in the growth rate of triploid and diploid fish. Gonadal development in both sexes was retarded in triploids at 5 months of age. Eggs fertilized with milt from triploids developed to gastrulation. Beyond gastrulation there was increasing mortality associated with abnormalities and none of them hatched. The display frequencies of air gulping, erection of operculum and fins, striking and biting, and undulating movements were fewer in triploids compared to diploids. It appears that triploids are less aggressive than diploids. The aggressive behaviour of fighting fish may be related Io their reproductive activity.