, H. L. , Y. W. , and H. P. The effects imply that Siamese fighting fish use gill flaring as an acute response in an effort to defend their territory; this reaction may get replaced by fin spreading as a chronic reaction, likely to reduce the active costs in the course of the contest. This week, the Fish of the Week title goes to the superbly flamboyant Siamese Fighting Fish Betta splendens, that is native to the Mekong Basin of Laos, Cambodia, Vietnam and Thailand. As an air respiratory fish, they’ll every so often be seen taking gulps of air from the floor of the water. The two sexes can be easily differentiated. Males have much larger fins than females and because of this, they are surprisingly bigger. Both male and feminine species can be found in a huge range of colours and variations, with some showing two toned styles like the male shown in this image.