Visual perception of texture in aggressive behavior of Betta splendens.

In order to elucidate the role of texture in fish vision, the agonistic behavior of male Siamese fighting fish (Betta splendens) was tested in a response to models composed by means of image processing techniques. Using the models with the contour shape of a side view of Betta splendens in an aggressive state, the responses were vigorous when there was a fine distribution of brightness and naturalistic color, producing textures like a scale pattern. Reactions became weaker as the brightness and color distribution reverted to more homogeneous levels and the scale pattern disappeared. When the artificial models with the circular contour shape were used, models with the scale pattern evoked more aggressive behaviors than those without it, while the existence of spherical gradation affected the behavior slightly. These results suggest that texture plays an important role in fish visual perception.